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Background: Inborn errors of glutathione metabolism may cause high anion gap metabolic acidosis due to pyroglutamic acid accumulation. Since 1988, cases of this acidosis have been reported in individuals without these defects. Methods: Given the poorly characterized predisposing factors, presentation, management, and prognosis of acquired pyroglutamic acidosis, we conducted a systematic review using the National Library of Medicine, Excerpta Medica, Web of Science, and Google Scholar databases. Results: A total of 131 cases were found. Most patients were females (79%), adults (92%) aged 51 years or older (66%) with pre-existing conditions (74%) such as undernutrition, alcohol-use disorder, or kidney disease, and had an ongoing infection (69%). The clinical features included diminished consciousness (60%), Kussmaul breathing (56%), and nausea or vomiting (27%). At least 92% of patients were on paracetamol therapy for >10 days at an appropriate dose, 32% on a β-lactamase-resistant penicillin, and 2.3% on vigabatrin. Besides severe anion gap acidosis, patients also presented with hypokalemia (24%) and kidney function deterioration (41%). Management involved discontinuing the offending drug (100%), bicarbonate (63%), acetylcysteine (42%), and acute kidney replacement therapy (18%). The fatality rate was 18%, which was higher without acetylcysteine (24%) compared to with it (11%). Conclusions: Acquired pyroglutamic acidosis is a rare, potentially fatal metabolic derangement, which usually occurs after paracetamol use, frequently combined with a β-lactamase-resistant penicillin or vigabatrin. This condition predominantly affects adults, especially women with factors like undernutrition, alcohol-use disorder, or kidney disease, often during infection. Increased awareness of this rare condition is necessary. [ABSTRACT FROM AUTHOR]

This review concerns the rare, acquired, usually iatrogenic, high-anion-gap metabolic acidosis, pyroglutamic acidosis. Pyroglutamate is a derivative of the amino acid glutamate, and is an intermediate in the 'glutathione cycle', by which glutathione is continuously synthesized and broken down. The vast majority of pyroglutamic acidosis cases occur in patients on regular, therapeutic doses of paracetamol. In about a third of cases, flucloxacillin is co-prescribed. In addition, the patients are almost always seriously unwell in other ways, typically with undernourishment of some form. Paracetamol, with underlying disorders, conspires to divert the glutathione cycle, leading to the overproduction of pyroglutamate. Hypokalaemia is seen in about a third of cases. Once the diagnosis is suspected, it is simple to stop the paracetamol and change the antibiotic (if flucloxacillin is present), pending biochemistry. N-acetyl-cysteine can be given, but while the biochemical justification is compelling, the clinical evidence base is anecdotal. [ABSTRACT FROM AUTHOR]

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant solid tumours, and abnormal metabolic reprogramming in the tumour microenvironment is regarded as an important contributor to its pathogenesis. As there is an urgency to identify new targets based on the metabolic features that are highly refractory to PDAC treatment, this study aimed to identify suitable therapeutic targets for PDAC. In this study, gene set enrichment and Kyoto Encyclopedia of Genes and Genomes analyses were performed on 163 PDAC tissue samples and 165 normal pancreatic tissue samples from The Cancer Genome Atlas and Genotype-Tissue Expression databases to identify alterations in critical metabolites that may contribute to PDAC pathogenesis. Furthermore, ultra-performance liquid chromatography–tandem mass spectrometry was performed to identify significant metabolic pathways between 24 pairs of tumour and adjacent non-tumour tissues and between serum samples from PDAC patients and healthy donors. Fifty-one tissue metabolites and 26 serum metabolites were altered in PDAC. Among them, those in the γ-glutamyl cycle were the most substantially changed, and 5-oxoproline was the biomarker of PDAC with the most significantly decreased levels. The γ-glutamyl cycle and 5-oxoproline might be potential biomarkers and therapeutic targets to improve the diagnosis, therapy, and prognosis of PDAC. [ABSTRACT FROM AUTHOR]

AbstractBackground Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant solid tumours, and abnormal metabolic reprogramming in the tumour microenvironment is regarded as an important contributor to its pathogenesis.Objectives As there is an urgency to identify new targets based on the metabolic features that are highly refractory to PDAC treatment, this study aimed to identify suitable therapeutic targets for PDAC.Methods In this study, gene set enrichment and Kyoto Encyclopedia of Genes and Genomes analyses were performed on 163 PDAC tissue samples and 165 normal pancreatic tissue samples from The Cancer Genome Atlas and Genotype-Tissue Expression databases to identify alterations in critical metabolites that may contribute to PDAC pathogenesis. Furthermore, ultra-performance liquid chromatography–tandem mass spectrometry was performed to identify significant metabolic pathways between 24 pairs of tumour and adjacent non-tumour tissues and between serum samples from PDAC patients and healthy donors.Results Fifty-one tissue metabolites and 26 serum metabolites were altered in PDAC. Among them, those in the γ-glutamyl cycle were the most substantially changed, and 5-oxoproline was the biomarker of PDAC with the most significantly decreased levels.Conclusions The γ-glutamyl cycle and 5-oxoproline might be potential biomarkers and therapeutic targets to improve the diagnosis, therapy, and prognosis of PDAC.

Venous thromboembolism is a serious problem because it significantly increases the risk of developing vascular complications in elderly patients with obesity or immobilization, cancer, and many other diseases. Thus, there is a need to study new therapeutic strategies, including new medicinal agents for the efficient and safe correction of thrombus disorders. In this work, we have synthesized a number of new amides and peptides of 4-amino-5-oxoprolines and studied their antiplatelet and antithrombotic activity in experiments in vitro and in vivo. It has been found that the newly obtained compounds slow down the process of thrombus formation in a model of arterial and venous thrombosis, without affecting plasma hemostasis parameters. (2S,4S)-4-Amino-1-(4-fluorophenyl)-5-oxoprolyl-(S)-phenylalanine proved to be the most efficient among the studied derivatives. The results obtained indicate the advisability of further studies on 5-oxoproline derivatives in order to design pharmaceutical agents for the prevention and treatment of the consequences of thrombosis. [ABSTRACT FROM AUTHOR]

A series of (2S,4S)-4-amino-N-arylpyroglutamic acids was first obtained by the nucleophilic substitution of bromine atom in dimethyl (2S,4RS)-4-bromo-N-phthaloylglutamate under the action of primary arylamines, followed by the separation of diastereomers and removal of protecting groups by acidic hydrolysis. These compounds were studied for anti-platelet and antithrombotic activity in experiments in vitro and in vivo. Some compounds were identified as exhibiting a significant effect on platelet function, which was manifested in slowing down the process of thrombus formation in the model of arterial and deep vein thrombosis. It was established that the most efficient compound is (2S,4S)-4-amino-N-(4-fluoro-phenyl)pyroglutamic acid, with its effect being comparable to that of acetylsalicylic acid. [ABSTRACT FROM AUTHOR]

Venous thromboembolism is a serious problem because it significantly increases the risk of developing vascular complications in elderly patients with obesity or immobilization, cancer, and many other diseases. Thus, there is a need to study new therapeutic strategies, including new medicinal agents for the efficient and safe correction of thrombus disorders. In this work, we have synthesized a number of new amides and peptides of 4-amino-5-oxoprolines and studied their antiplatelet and antithrombotic activity in experiments in vitro and in vivo. It has been found that the newly obtained compounds slow down the process of thrombus formation in a model of arterial and venous thrombosis, without affecting plasma hemostasis parameters. (2S,4S)-4-Amino-1-(4-fluorophenyl)-5-oxoprolyl-(S)-phenylalanine proved to be the most efficient among the studied derivatives. The results obtained indicate the advisability of further studies on 5-oxoproline derivatives in order to design pharmaceutical agents for the prevention and treatment of the consequences of thrombosis.

OBJECTIVES: Current standard of care imaging, cytology, or cystic fluid analysis cannot reliably differentiate malignant from benign pancreatic cystic neoplasms. This study sought to determine if the metabolic profile of cystic fluid could distinguish benign and malignant lesions, as well as mucinous and non-mucinous lesions. Methods: Metabolic profiling by untargeted mass spectrometry and quantitative nuclear magnetic resonance was performed in 24 pancreatic cyst fluid from surgically resected samples with pathological diagnoses and clinicopathological correlation. Results: (Iso)-butyrylcarnitine distinguished malignant from benign pancreatic cysts, with a diagnostic accuracy of 89%. (Iso)-butyrylcarnitine was 28-fold more abundant in malignant cyst fluid compared with benign cyst fluid (P=.048). Furthermore, 5-oxoproline (P=.01) differentiated mucinous from non-mucinous cysts with a diagnostic accuracy of 90%, better than glucose (82% accuracy), a previously described metabolite that distinguishes mucinous from non-mucinous cysts. Combined analysis of glucose and 5-oxoproline did not improve the diagnostic accuracy. In comparison, standard of care cyst fluid carcinoembryonic antigen (CEA) and cytology had a diagnostic accuracy of 40% and 60% respectively for mucinous cysts. (Iso)-butyrylcarnitine and 5-oxoproline correlated with cyst fluid CEA levels (P 3 cm, ≥ 1 high-risk features, cyst fluid CEA, and cytology are 38%, 75%, 80%, and 75%, respectively. Conclusions: (Iso)-butyrylcarnitine has potential clinical application for accurately distinguishing malignant from benign pancreatic cysts, and 5-oxoproline for distinguishing mucinous from non-mucinous cysts.

Rationale & Objective: Novel metabolite biomarkers of kidney failure with replacement therapy (KFRT) may help identify people at high risk for adverse kidney outcomes and implicated pathways may aid in developing targeted therapeutics. Study Design: Prospective cohort. Setting & Participants: The cohort included 3,799 Atherosclerosis Risk in Communities study participants with serum samples available for measurement at visit 1 (1987-1989). Exposure: Baseline serum levels of 318 metabolites. Outcomes: Incident KFRT, kidney failure (KFRT, estimated glomerular filtration rate

5-Oxoproline (OP) is well-known as an enzymatic intermediate in the eukaryotic γ-glutamyl cycle, but it is also an unavoidable damage product formed spontaneously from glutamine and other sources. Eukaryotes metabolize OP via an ATP-dependent 5-oxoprolinase; most prokaryotes lack homologs of this enzyme (and the γ-glutamyl cycle) but are predicted to have some way to dispose of OP if its spontaneous formation in vivo is significant. Comparative analysis of prokaryotic genomes showed that the gene encoding pyroglutamyl peptidase, which removes N-terminal OP residues, clusters in diverse genomes with genes specifying homologs of a fungal lactamase (renamed prokaryotic 5-oxoprolinase A, pxpA) and homologs of allophanate hydrolase subunits (renamed pxpB and pxpC). Inactivation of Bacillus subtilis pxpA, pxpB, or pxpC genes slowed growth, caused OP accumulation in cells and medium, and prevented use of OP as a nitrogen source. Assays of cell lysates showed that ATP-dependent 5-oxoprolinase activity disappeared when pxpA, pxpB, or pxpC was inactivated. 5-Oxoprolinase activity could be reconstituted in vitro by mixing recombinant B. subtilis PxpA, PxpB, and PxpC proteins. In addition, overexpressing Escherichia coli pxpABC genes in E. coli increased 5-oxoprolinase activity in lysates ≥1700-fold. This work shows that OP is a major universal metabolite damage product and that OP disposal systems are common in all domains of life. Furthermore, it illustrates how easily metabolite damage and damage-control systems can be overlooked, even for central metabolites in model organisms.

Abstract Intelligence predicts important life and health outcomes, but the biological mechanisms underlying differences in intelligence are not yet understood. The use of genetically determined metabotypes (GDMs) to understand the role of genetic and environmental factors, and their interactions, in human complex traits has been recently proposed. However, this strategy has not been applied to human intelligence. Here we implemented a two-sample Mendelian randomization (MR) analysis using GDMs to assess the causal relationships between genetically determined metabolites and human intelligence. The standard inverse-variance weighted (IVW) method was used for the primary MR analysis and three additional MR methods (MR-Egger, weighted median, and MR-PRESSO) were used for sensitivity analyses. Using 25 genetic variants as instrumental variables (IVs), our study found that 5-oxoproline was associated with better performance in human intelligence tests (PIVW = 9.25 × 10–5). The causal relationship was robust when sensitivity analyses were applied (PMR-Egger = 0.0001, PWeighted median = 6.29 × 10–6, PMR-PRESSO = 0.0007), and repeated analysis yielded consistent result (PIVW = 0.0087). Similarly, also dihomo-linoleate (20:2n6) and p-acetamidophenylglucuronide showed robust association with intelligence. Our study provides novel insight by integrating genomics and metabolomics to estimate causal effects of genetically determined metabolites on human intelligence, which help to understanding of the biological mechanisms related to human intelligence.

Bone marrow mesenchymal stem cells (BMSCs) have been shown to promote stroke recovery, however, the underlying mechanisms are not well understood. In this study naïve rats were intravenously injected with syngeneic BMSCs to screen for potential differences in brain metabolite spectrum versus vehicle-treated controls by capillary electrophoresis-mass spectrometry. A total of 65 metabolites were significantly changed after BMSC treatment. Among them, 5-oxoproline, an intermediate in the biosynthesis of the endogenous glutathione (GSH), was increased. To confirm the obtained results and investigate the metabolic pathways, BMSCs were injected into rats 24 h after middle cerebral artery occlusion (MCAO). Rats receiving vehicle solution and sham-operated animals served as controls. High performance liquid chromatography, reverse transcription-quantitative polymerase chain reaction, and Western blotting revealed that intravenous BMSC application increased the levels of 5-oxoproline and GSH in MCAO rats, as well as the expression of key enzymes involved in GSH synthesis including, gamma-glutamylcyclotransferase and gamma-glutamylcysteine ligase. Subsequent clinical investigation confirmed that acute ischemic stroke patients had higher plasma 5-oxoproline and GSH levels than age- and sex-matched non-stroke controls. The optimal cutoff value for 5-oxoproline diagnosing acute ischemic stroke (≤ 7d) was 3.127 µg/mL (sensitivity, 63.4 %; specificity, 81.2 %) determined by receiver characteristic operator curve. The area under the curve was 0.782 (95 % confidence interval: 0.718–0.845). Our findings indicate that BMSCs play a protective role in ischemic stroke through upregulation of GSH and 5-oxoproline is a potential biomarker for acute ischemic stroke. Ischemic stroke causes oxidative stress and induction of endogenous, glutathione-dependent anti-oxidative mechanisms. 5-oxoproline, an important metabolite in glutathione biosynthesis, could serve as a biomarker of acute ischemic stroke. Moreover, intravenous bone marrow mesenchymal stem cell (BMSC) treatment after experimental stroke upregulates the expression of key enzymes involved in glutathione synthesis, which results in better antioxidative defense and improved stroke outcome. [ABSTRACT FROM AUTHOR]

Introduction: Inherited 5-oxoprolinase (OPLAH) deficiency is a rare inborn condition characterized by 5-oxoprolinuria. The inherited condition of 5-oxoprolinuria, or pyroglutamic aciduria, is primarily caused by mutations in the genes that encode glutathione synthetase (GSS) and 5-oxoprolinase (OPLAH), which are enzymes involved in the gamma-glutamyl cycle in glutathione metabolism. We report a 3-year-old male patient with epilepsy and speech difficulty diagnosed as primary 5-oxoprolinuria due to a novel OPLAH gene mutation., Case Presentation: A 3-year-old boy who was delivered at full term in an uncomplicated birth to consanguineous parents presented with epilepsy at the age of 2 years. He did not speak fluently. He was using 5-10 words with decreased language fluency. His past medical history revealed postnatal macrocephaly, hydrocephalus, and well-controlled epilepsy with levetiracetam. Progressive cerebral atrophy, hypomyelination, ventriculomegaly, and corpus callosum hypoplasia were striking features in brain MRI. A urine sample was sent for organic acid analysis by gas chromatography-mass spectrometry (GC-MS); quantitation of 5-oxoproline by stable isotope dilution gave a value of 177.9 mmol/mol creatinine (reference values 25.8-92.2). Molecular genetic analysis of the OPLAH gene revealed a novel homozygous variant ( OPLAH (NM_017570.5): c.1909C>T p.Arg637Trp)., Conclusion: We conclude that inherited 5-oxoprolinase deficiency is not a benign biochemical condition, and patients with 5-oxoprolinuria should be screened for it. The nature of this inherited metabolic disorder must be determined through long-term observation. We wish to emphasize the significance of molecular genetic analysis in symptomatic patients with persistently elevated levels of 5-oxoproline in the urine, as measured by organic acid analysis., Competing Interests: The authors have no conflicts of interest to declare., (© 2024 S. Karger AG, Basel.)

Current standard of care imaging, cytology, or cystic fluid analysis cannot reliably differentiate malignant from benign pancreatic cystic neoplasms. This study sought to determine if the metabolic profile of cystic fluid could distinguish benign and malignant lesions, as well as mucinous and non-mucinous lesions. Metabolic profiling by untargeted mass spectrometry and quantitative nuclear magnetic resonance was performed in 24 pancreatic cyst fluid from surgically resected samples with pathological diagnoses and clinicopathological correlation. (Iso)-butyrylcarnitine distinguished malignant from benign pancreatic cysts, with a diagnostic accuracy of 89%. (Iso)-butyrylcarnitine was 28-fold more abundant in malignant cyst fluid compared with benign cyst fluid (P =.048). Furthermore, 5-oxoproline (P =.01) differentiated mucinous from non-mucinous cysts with a diagnostic accuracy of 90%, better than glucose (82% accuracy), a previously described metabolite that distinguishes mucinous from non-mucinous cysts. Combined analysis of glucose and 5-oxoproline did not improve the diagnostic accuracy. In comparison, standard of care cyst fluid carcinoembryonic antigen (CEA) and cytology had a diagnostic accuracy of 40% and 60% respectively for mucinous cysts. (Iso)-butyrylcarnitine and 5-oxoproline correlated with cyst fluid CEA levels (P <.0001 and P <.05 respectively). For diagnosing malignant pancreatic cysts, the diagnostic accuracies of cyst size > 3 cm, ≥ 1 high-risk features, cyst fluid CEA, and cytology are 38%, 75%, 80%, and 75%, respectively. (Iso)-butyrylcarnitine has potential clinical application for accurately distinguishing malignant from benign pancreatic cysts, and 5-oxoproline for distinguishing mucinous from non-mucinous cysts. [ABSTRACT FROM AUTHOR]

Caprolactamase is the first enzyme in the caprolactam degradation pathway of Pseudomonas jessenii. It is composed of two subunits (CapA and CapB) and sequence‐related to other ATP‐dependent enzymes involved in lactam hydrolysis, like 5‐oxoprolinases and hydantoinases. Low sequence similarity also exists with ATP‐dependent acetone‐ and acetophenone carboxylases. The caprolactamase was produced in Escherichia coli, isolated by His‐tag affinity chromatography, and subjected to functional and structural studies. Activity toward caprolactam required ATP and was dependent on the presence of bicarbonate in the assay buffer. The hydrolysis product was identified as 6‐aminocaproic acid. Quantum mechanical modeling indicated that the hydrolysis of caprolactam was highly disfavored (ΔG0'= 23 kJ/mol), which explained the ATP dependence. A crystal structure showed that the enzyme exists as an (αβ)2 tetramer and revealed an ATP‐binding site in CapA and a Zn‐coordinating site in CapB. Mutations in the ATP‐binding site of CapA (D11A and D295A) significantly reduced product formation. Mutants with substitutions in the metal binding site of CapB (D41A, H99A, D101A, and H124A) were inactive and less thermostable than the wild‐type enzyme. These residues proved to be essential for activity and on basis of the experimental findings we propose possible mechanisms for ATP‐dependent lactam hydrolysis. [ABSTRACT FROM AUTHOR]

Glutathione synthetase (GSS) deficiency is a rare disorder, occurring with a frequency of less than 1 in 100,000 individuals worldwide. The clinical presentation may vary from mild to severe, and manifestations include hemolytic anemia, hyperbilirubinemia, metabolic acidosis, neurological problems, and sepsis. Herein, we present a case of a newborn boy with the most severe phenotype of GSS deficiency, diagnosed based on clinical features and increased urinary 5-oxoproline levels determined via gas chromatography mass spectrometry (GCMS) testing. [ABSTRACT FROM AUTHOR]

A rare complication, 5-oxoproline-induced high anion gap metabolic acidosis (HAGMA) is associated with chronic acetaminophen use, predominantly reported in outpatient settings. However, its occurrence in hospitalized patients, particularly those with end-stage renal disease (ESRD), remains underreported. We present a case of a 74-year-old female with ESRD on hemodialysis who developed HAGMA highly suspicious for 5-oxoproline toxicity from acetaminophen usage following cardiac surgery. Despite a standard analgesic dose, the patient's renal impairment likely predisposed her to 5-oxoproline accumulation, resulting in severe metabolic acidosis. Discontinuation of acetaminophen led to the resolution of HAGMA, highlighting the importance of recognizing this rare but potentially life-threatening complication in the inpatient and critical care setting. This case suggests a potential interaction between acetaminophen metabolism and renal dysfunction in the pathogenesis of 5-oxoproline-induced HAGMA., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Kwon et al.)

Acetaminophen and flucloxacillin both interfere with the ?-glutamyl cycle. Long-lasting concomitant use of flucloxacillin and acetaminophen can lead to 5-oxoproline accumulation and severe high anion gap metabolic acidosis. Females and patients with sepsis, impaired kidney and/or liver function, malnutrition, advanced age, congenital 5-oxoprolinase deficiency and supratherapeutic acetaminophen and flucloxacillin dosage are associated with increased risk. Therefore, a critical attitude towards the prescription of acetaminophen concomitant with flucloxacillin in these patients is needed. We present the case of a 79-year-old woman with severe 5-oxoprolinaemia after long-lasting treatment with flucloxacillin and acetaminophen, explaining the toxicological mechanism and risk factors, and we make recommendations for acetaminophen use in patients with long-lasting flucloxacillin treatment.

1-Substituted (2S,4S)-4-amino-5-oxoprolines have been obtained by nucleophilic substitution of bromine in dimethyl (2S,4RS)-4-bromo-N-phthaloylglutamate followed by isolation of the predominant (2S,4S)-diastereomer and removal of protecting groups. The psychotropic activity of the obtained compounds has been studied after a single administration in experimental animals. 4-Amino-1-(4-bromophenyl)-5-oxoproline and especially 4-amino-1-(4-aminophenyl)-5-oxoproline showed pronounced anxiolytic activity in the Elevated plus maze test. (2S,4S)-4-Amino-5-oxoprolines containing 4-methylphenyl, 4-bromophenyl, 4‑aminophenyl, and 2,3-dimethyl-5-oxo-1-phenyl-3-pyrazolin-4-yl substituents at the 1-position exhibited nootropic activity: they improved the formation and retention of the memory trace in the Passive avoidance test and the Active avoidance test (Extrapolation escape test). [ABSTRACT FROM AUTHOR]

Introduction: Several reports describe high anion gap metabolic acidosis with 5-oxoproline (5-OP) after acetaminophen exposure, including therapeutic use of acetaminophen. The mechanism may involve disordered glutathione metabolism. It is unknown whether acute acetaminophen overdose consistently causes elevations in 5-oxoproline concentration. Methods: We enrolled 23 consecutive adult and adolescent patients with measureable plasma APAP after acute APAP overdose. We used plasma left over in the laboratory after blood tests obtained in clinical care of the patients. We measured plasma [5-OP] by GC/MS. We compared the [5-OP] to laboratory results obtained in the care of these patients to search for correlations. The study had IRB approval. Results: Eighteen patients had non-detectable or normal (<100 μmol/L) 5-oxoproline concentrations. Six more patients had concentrations between 100 μmol/L and 300 μmol/L. There was no significant correlation of 5-OP with APAP, AST, ALT, creatinine, anion gap, INR, or total bilirubin. Discussion: Limitations of the study include small sample size and treatment with IV N-acetylcysteine for all patients with APAP concentrations above the 150 line of the Rumack Matthew nomogram or with hepatotoxicity. We believe that inherited enzyme deficiencies more likely explain cases of 5-oxoprolinemia. Conclusion: Acetaminophen overdose generally results in normal 5-oxoproline concentrations with some patients having slightly elevated 5-oxoproline concentrations. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) contributes to redox maintenance and detoxification of various xenobiotic and endogenous substances. γ-glutamyl cyclotransferase (ChaC) is involved in GSH degradation. However, the molecular mechanism underlying GSH degradation in silkworms (Bombyx mori) remains unknown. Silkworms are lepidopteran insects that are considered to be an agricultural pest model. We aimed to examine the metabolic mechanism underlying GSH degradation mediated by B. mori ChaC and successfully identified a novel ChaC gene in silkworms (herein, bmChaC). The amino acid sequence and phylogenetic tree revealed that bmChaC was closely related to mammalian ChaC2. We overexpressed recombinant bmChaC in Escherichia coli, and the purified bmChaC showed specific activity toward GSH. Additionally, we examined the degradation of GSH to 5-oxoproline and cysteinyl glycine via liquid chromatography-tandem mass spectrometry. Quantitative real-time polymerase chain reaction revealed that bmChaC mRNA expression was observed in various tissues. Our results suggest that bmChaC participates in tissue protection via GSH homeostasis. This study provides new insights into the activities of ChaC and the underlying molecular mechanisms that can aid the development of insecticides to control agricultural pests., (© 2023 Wiley Periodicals LLC.)

Résumé On retient parmi les causes classiques d’acidose métabolique à trou anionique augmenté (AMTAA) les acidoses lactiques ou cétosiques, la réduction néphronique (insuffisance rénale sans acidose tubulaire) et certaines intoxications. Néanmoins, le clinicien peut être confronté à certains cas d’AMTAA inexpliqués, nécessitant la recherche d’étiologies plus rares. Nous décrivons le cas d’un patient de 79 ans ayant présenté une acidose liée à l’accumulation de 5-oxoproline (acide pyroglutamique) secondaire à la prise chronique de paracétamol. La physiopathologie de ce trouble est liée à des anomalies du cycle du gamma-glutamyl causées par la prise de paracétamol sur un terrain de comorbidités sévères, conduisant à l’accumulation de 5-oxoproline. Devant une AMTAA chez un patient présentant des comorbidités et dont le traitement comporte du paracétamol, une acidose à l’acide pyroglutamique devrait être suspectée quand les causes usuelles ont été écartées. Ce diagnostic, bien que rare, devrait être présent à l’esprit du clinicien car le simple arrêt du paracétamol permet la résolution de cette anomalie. The most common causes of high anion gap metabolic acidosis (HAGMA) are lactic acidosis, ketoacidosis, and intoxications. Nevertheless, clinicians can be faced with unexplained HAGMA, with a need to look for less common etiologies. We describe a case of 5-oxoproline (pyroglutamate) acidosis due to chronic acetaminophen ingestion at therapeutic dose in a 79-year-old inpatient. The pathophysiology of this condition is detailed, with abnormalities in the gamma-glutamyl cycle due to acetaminophen ingestion and severe chronic morbidities, resulting in glutathione and cysteine deficiency and then accumulation of 5-oxoproline. In HAGMA, when usual causes have been excluded, 5-oxoproline acidosis should be suspected in patients with chronic morbidities and acetaminophen ingestion. This diagnosis should be kept in mind because it generally resolves quickly with cessation of acetaminophen and administration of intravenous fluids. [ABSTRACT FROM AUTHOR]

4-Oxalocrotonate tautomerase (4-OT) catalyzes the enol-keto tautomerization of 2-hydroxymuconate, utilizing its N-terminal proline (Pro-1) as general base catalyst. Substituting Pro-1 with bulky or charged residues will result in poor or no post-translational removal of the translation-initiating methionine by the methionine aminopeptidase (MetAP) of the Escherichia coli expression host. Here, we set out to investigate whether co-expression with previously engineered aminopeptidase MetAP-∗TG can be used to produce the P1S, P1H and P1Q variants of 4-OT in a demethionylated form. The P1S variant, which carries a small residue at the penultimate position (the first position after the initiating methionine), was found to be fully processed by wild-type MetAP. The P1S variant has low-level 2-hydroxymuconate tautomerase and promiscuous oxaloacetate decarboxylase activity. The P1Q and P1H variants of 4-OT, which carry bulky residues at the penultimate position, could only be obtained in a demethionylated form (a minor fraction of the purified protein is still composed of methionylated enzyme) by co-expression with MetAP-∗TG. Interestingly, the Gln-1 residue of the demethionylated P1Q variant undergoes intramolecular cyclization to form pyroglutamate (pE), yielding variant P1pE. Whereas the P1H/M1P2H mixture has low-level tautomerase activity, the P1pE/M1P2Q mixture has robust tautomerase activity. The substitution of Pro-1 by Gln, followed by removal of the initiating Met and cyclization of Gln-1 to form pE, is a unique way to obtain a structural analogue of proline on the N-terminus of 4-OT. This opens up new possibilities to study the importance of Pro-1 in recently discovered C–C bond-forming activities of this highly promiscuous tautomerase.

Purpose: A patient was identified with severe metabolic acidosis, a high anion gap and 5-oxoproline accumulation, probably caused by the simultaneous use of paracetamol (acetaminophen) and flucloxacillin. We wanted to investigate the necessity to control the interaction between both drugs with an automatic alert system. Methods: To investigate the relevance of the interaction of paracetamol and flucloxacillin, a retrospective study was conducted. Data on paracetamol and flucloxacillin prescriptions and laboratory data (pH, Na, HCO , Cl, albumin and 5-oxoproline levels) were combined to assess the prevalence of acidosis, calculate the anion gap and analyse 5-oxoproline levels in clinically admitted patients using both drugs simultaneously. Results: In the 2-year study period, approximately 53,000 admissions took place in our hospital. One thousand and fifty-seven patients used paracetamol and flucloxacillin simultaneously, of which 51 patients (4.8%) had a serum pH ≤ 7.35. One patient, the same patient as presented in the case report, had a high anion gap and a toxic level of 5-oxoproline. Conclusion: The prevalence of metabolic acidosis is very low and the only patient identified with the interaction was recognised during normal clinical care. We conclude that automatic alerts based on simultaneous use of paracetamol and flucloxacillin will generate too many signals. To recognise patients earlier and prevent severe outcomes, a warning system (clinical rule) based on paracetamol, flucloxacillin and pH measurement may be helpful. Early calculation of the anion gap can narrow the differential diagnosis of patients with metabolic acidosis and measurement of 5-oxoproline can explain acidosis due the interaction of paracetamol and flucloxacillin. [ABSTRACT FROM AUTHOR]

High anion gap metabolic acidosis frequently complicates acute paracetamol overdose and is generally attributed to lactic acidosis or compromised hepatic function. However, metabolic acidosis can also be caused by organic acid 5-oxoproline (pyroglutamic acid). Paracetamol’s toxic intermediate, N-acetyl- p -benzoquinoneimine irreversibly binds to glutathione and its depletion leads to subsequent disruption of the gamma glutamyl cycle and an excessive 5-oxoproline generation. This is undoubtedly an underdiagnosed condition because measurement of serum 5-oxoproline level is not readily available. A simple, cost effective, and fast capillary electrophoresis method with diode array detection (DAD) for simultaneous measurement of both paracetamol (acetaminophen) and 5-oxoproline in serum was developed and validated. This method is highly suitable for clinical toxicology laboratory diagnostic, allowing rapid quantification of acidosis inducing organic acid 5-oxoproline present in cases of paracetamol overdose. The calibration dependence of the method was proved to be linear in the range of 1.3–250 μg mL −1 , with adequate accuracy (96.4–107.8%) and precision (12.3%). LOQ equaled 1.3 μg mL −1 for paracetamol and 4.9 μg mL −1 for 5-oxoproline. [ABSTRACT FROM AUTHOR]

Long-term use of paracetamol (at therapeutic doses) can cause the accumulation of endogenous organic pyroglutamate, resulting in metabolic acidosis with an elevated anion gap. This occurs in the presence of malnutrition, infection, antibiotic use, renal failure and pregnancy. Given the prevalence of these risk factors, this condition is thought to be relatively common in a hospitalised population but is probably significantly underdiagnosed. Prompt recognition is essential because the condition is entirely reversible if the causative agents are withdrawn. Here we describe five cases of pyroglutamic acidosis that we have encountered in a tertiary referral hospital. Together they illustrate the common clinical risk factors and the excellent prognosis, once a diagnosis is made. We describe how a rudimentary acid-base analysis (calculation of the anion gap) usually leads to the diagnosis but how a more nuanced approach may be required in the presence of mixed acid-base disorders. [ABSTRACT FROM AUTHOR]

Solute carrier (SLC) 16A1 is a pH-dependent carrier of 5-oxoproline, a derivative of the amino acid. SLC16A1 interacts with carboxylate group-containing substrates, which are also present in atorvastatin, and might be the reason for its ability to interact with atorvastatin. Does atorvastatin interact with the carrier? Does it also interact with the carrier via the substrate recognition site? This study was carried out to answer these questions. Polymerase chain reaction was used to determine the expression of SLC16A1 in normal human astrocytes. We induced SLC16A1 expression in a mammalian cell line and in Xenopus laevis oocytes. We used [ 3 H] 5-oxoproline for direct measurement of SLC16A1-specific transport activity. SLC16A1 was clearly observed in normal human astrocytes. 3-Hydroxy-3-methyl-glutaryl-CoA reductase inhibitors inhibited the SLC16A1-specific transport of 5-oxoproline. Atorvastatin was the most potent inhibitor, with an inhibition constant of 40 μM. The drug was a non-competitive inhibitor of SLC16A1. In the present study, we showed non-competitive inhibition of SLC16A1-specific transport activity by atorvastatin. However, the affinity between the drug and the carrier was extremely low. Therefore, the interaction of atorvastatin with SLC16A1 is unlikely to be a problem in clinical practice. [ABSTRACT FROM AUTHOR]

Unlabelled: Transient 5-oxoprolinuria is a phenomenon that is well recognised in adults. We illustrate an unusual paediatric case of transient 5-oxoprolinuria presenting during an episode of severe sepsis with concomitant paracetamol use. The 15-month-old patient had an extremely high anion gap metabolic acidosis. Adequate resuscitation failed to correct the biochemical disturbance, and high levels of 5-oxoproline were identified. A combination of haemofiltration, replenishment of glutathione stores with N-acetylcysteine and cessation of paracetamol administration resulted in the resolution of the acidosis. Subsequent testing following treatment of the sepsis revealed no ongoing 5-oxoprolinuria.Conclusion: Transient 5-oxoprolinuria has been previously reported in the adult population during episodes of severe sepsis and various pharmaceutical interventions. This case illustrates that it is a phenomenon that should be considered in paediatric patients where a very high anion gap metabolic acidosis exists that cannot be explained by the biochemical indices.What Is Known: • 5-oxoprolinuria in the paediatric population is usually secondary to an inborn error of metabolism. • Transient 5-oxoprolinuria is well recognised in adults during episodes of severe glutathione depletion.What Is New: • Transient 5-oxoprolinuria is a phenomenon rarely reported in the paediatric population. • It highlights the importance of investigating a high anion gap such that unusual diagnoses are not missed. [ABSTRACT FROM AUTHOR]

Introduction 5-oxoproline (pyroglutamic acid), an organic acid intermediate of the gamma-glutamyl cycle, is a rare cause of high anion gap metabolic acidosis. Acetaminophen and several other drugs have been implicated in the development of transient 5-oxoprolinemia in adults. We believe that reporting all cases of 5-oxoprolinemia will contribute to a better understanding of this disease. Here, we report the case of a patient who developed transient 5-oxoprolinemia following therapeutic acetaminophen use. Case presentation A 75-year-old Caucasian woman was initially admitted for treatment of an infected hip prosthesis and subsequently developed transient high anion gap metabolic acidosis. Our patient received 40g of acetaminophen over a 10-day period. After the more common causes of high anion gap metabolic acidosis were excluded, a urinary organic acid screen revealed a markedly increased level of 5-oxoproline. The acidosis resolved completely after discontinuation of the acetaminophen. Conclusion 5-oxoproline acidosis is an uncommon cause of high anion gap metabolic acidosis; however, it is likely that it is under-diagnosed as awareness of the condition remains low and testing can only be performed at specialized laboratories. The diagnosis should be suspected in cases of anion gap metabolic acidosis, particularly in patients with recent acetaminophen use in combination with sepsis, malnutrition, liver disease, pregnancy or renal failure. This case has particular interest in medicine, especially for the specialties of nephrology and orthopedics. We hope that it will add more information to the literature about this rare condition. [ABSTRACT FROM AUTHOR]

4-Oxalocrotonate tautomerase (4-OT) catalyzes the enol-keto tautomerization of 2-hydroxymuconate, utilizing its N-terminal proline (Pro-1) as general base catalyst. Substituting Pro-1 with bulky or charged residues will result in poor or no post-translational removal of the translation-initiating methionine by the methionine aminopeptidase (MetAP) of the Escherichia coli expression host. Here, we set out to investigate whether co-expression with previously engineered aminopeptidase MetAP-∗TG can be used to produce the P1S, P1H and P1Q variants of 4-OT in a demethionylated form. The P1S variant, which carries a small residue at the penultimate position (the first position after the initiating methionine), was found to be fully processed by wild-type MetAP. The P1S variant has low-level 2-hydroxymuconate tautomerase and promiscuous oxaloacetate decarboxylase activity. The P1Q and P1H variants of 4-OT, which carry bulky residues at the penultimate position, could only be obtained in a demethionylated form (a minor fraction of the purified protein is still composed of methionylated enzyme) by co-expression with MetAP-∗TG. Interestingly, the Gln-1 residue of the demethionylated P1Q variant undergoes intramolecular cyclization to form pyroglutamate (pE), yielding variant P1pE. Whereas the P1H/M1P2H mixture has low-level tautomerase activity, the P1pE/M1P2Q mixture has robust tautomerase activity. The substitution of Pro-1 by Gln, followed by removal of the initiating Met and cyclization of Gln-1 to form pE, is a unique way to obtain a structural analogue of proline on the N-terminus of 4-OT. This opens up new possibilities to study the importance of Pro-1 in recently discovered C–C bond-forming activities of this highly promiscuous tautomerase. [ABSTRACT FROM AUTHOR]

Rationale: The metabolic acidoses are generally separated into 2 categories on the basis of an anion gap calculation: high-anion-gap and normal anion-gap metabolic acidosis. When a high-anion-gap metabolic acidosis (HAGMA) is not clearly explained by common etiologies and routine confirmatory testing, specialized testing can definitively establish rare diagnoses such as 5-oxoproline, d-lactate accumulation, or diethylene glycol toxicity., Presenting Concerns of the Patient: A 56-year-old woman had a prolonged hospital admission following perforated diverticulitis requiring sigmoid resection. Her hospitalization was complicated by feculent peritonitis and surgical wound dehiscence needing prolonged broad-spectrum antibiotics and wound debridements. She developed acute kidney injury and HAGMA in the hospital., Diagnoses: Chart review showed that she received a large cumulative dose of acetaminophen during her hospital stay. Laboratory studies showed markedly increased serum 5-oxoproline causing HAGMA., Interventions Including Prevention and Lifestyle: Patient was admitted to the intensive care unit and treated with N -acetylcysteine and renal replacement therapy., Outcomes: After admission to the intensive care unit, the patient continued to require vasopressor and ventilatory support for septic shock and a ventilator-associated pneumonia. After an initial recovery and resolution of her HAGMA, she subsequently suffered recurrent aspirations which were fatal., Teaching Points: 1. The acronym GOLD MARK is useful when assessing patients with HAGMA and most causes of HAGMA can be established with routine testing.2. When the etiology of HAGMA remains unclear, additional testing can be required to diagnose rare causes of HAGMA.3. Rare causes of HAGMA are diethylene glycol, 5-oxoproline, and d-lactate accumulation.4. Acidosis secondary to 5-oxoproline accumulation can occur even with "therapeutic" doses of acetaminophen in patients receiving it regularly for a prolonged period and who have depleted glutathione stores.5. Risk factors for glutathione depletion include malnutrition, older age, sepsis, pregnancy, multiple chronic illnesses, and chronic kidney disease., Competing Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Ana Cecilia Farfan Ruiz—none; Sriram Sriperumbuduri—none; Julie L V Shaw—none; Edward G Clark—Editorial Board of CJKHD. All authors declared no competing interest., (© The Author(s) 2022.)

Context. Paracetamol (acetaminophen) ingestion is the most frequent pharmaceutical overdose in the developed world. Metabolic acidosis sometimes occurs, but the acidosis is infrequently persistent or severe. A growing number of case reports and case series describe high anion gap metabolic acidosis (HAGMA) following paracetamol exposure with subsequent detection or measurement of 5-oxoproline (also called pyroglutamic acid) in blood, urine, or both. Typically 5-oxoprolinuria or 5-oxoprolinemia occurs in the setting of inborn genetic errors in glutathione metabolism. It is unknown whether 5-oxoprolinemia in the setting of paracetamol exposure reflects an acquired or transient derangement of glutathione metabolism or previously unrecognized genetic defects. Objective. We reviewed the published cases of 5-oxoprolinemia or 5-oxoprolinuria among patients with HAGMA in the setting of paracetamol exposure. Our goal was to identify any consistent features that might increase our understanding of the pathophysiology, diagnosis, and treatment of similar cases. Methods. We searched the medical literature using PUBMED and EMBASE from inception to 28 August 2013 applying search terms ('oxoproline' OR 'pyroglutamic acid' AND 'paracetamol' OR 'acetaminophen'). The intersection of these two searches returned 77 articles, of which 64 involved human subjects and were in English. Two articles, one each in Spanish and Dutch, were reviewed. An additional Google Scholar search was done with the same terms. We manually searched the reference lists of retrieved articles to identify additional four relevant articles. We focused on articles including measured 5-oxoproline concentrations in urine or blood. Results. Twenty-two articles included quantified 5-oxoproline concentrations. Several additional articles mentioned only qualitative detection of 5-oxoproline in urine or blood without concentrations being reported. Our manual reference search yielded four additional articles for a total of 24 articles describing 43 patients with quantified 5-oxoproline concentrations. The cases varied widely in paracetamol dose, duration and circumstances of paracetamol exposure, presence, and degree of elevation in transaminase activities, and when reported observed blood, serum, or urine 5-oxoproline concentrations. Concomitant use of flucloxacillin, another medication associated with oxoprolinemia or oxoprolinuria, confounded several of the cases. No clear dose-response relationship existed between the quantity of paracetamol ingested and the observed concentrations of 5-oxoproline. Clinical outcomes, including mortality, varied with no clear relationship to 5-oxoproline concentrations. Conclusions. In rare cases, HAGMA in the setting of paracetamol exposure is attributable to 5-oxoprolinemia. Clinicians should first exclude commoner and treatable causes of HAGMA, such as lactic acidosis, co-ingested drug administration, and ketoacidosis. It is likely that the propensity for HAGMA following paracetamol exposure may be genetically determined. The effects of acetylcysteine on 5-oxoproline concentrations or clinical outcome are unknown. When HAGMA is diagnosed, the 5-oxoproline concentration and the glutathione synthetase activity should be measured. [ABSTRACT FROM AUTHOR]

Abstract: Background: Tuberculosis (TB) is a serious world-wide health problem, causing millions of deaths every year. Metabolomics is a relatively new approach to identify disease specific biomarkers. However, there is little information available on metabolite biomarkers in TB. In this study, we used gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) to identify serum metabolite biomarkers associated with the active state of TB. Methods: Potential biomarkers were selected by comparing serum metabolites in 10 healthy donors with 10TB patients, and in 6TB patients before and after treatment. Selected biomarkers were then validated using a larger population of samples from 120 healthy donors and 120TB patients derived from different clinical backgrounds Results: The 5-oxoproline level was consistently low in patients with active TB. Further validation in larger population of clinical samples showed that 5-oxoproline was associated with pathological damage of the lung but not with age, sex, or bacterial burden in TB patients. Conclusions: Serum 5-oxoproline may be a useful biomarker for active TB and pathological damage of the lung. [Copyright &y& Elsevier]

Rationale & Objective: Novel metabolite biomarkers of kidney failure with replacement therapy (KFRT) may help identify people at high risk for adverse kidney outcomes and implicated pathways may aid in developing targeted therapeutics., Study Design: Prospective cohort., Setting & Participants: The cohort included 3,799 Atherosclerosis Risk in Communities study participants with serum samples available for measurement at visit 1 (1987-1989)., Exposure: Baseline serum levels of 318 metabolites., Outcomes: Incident KFRT, kidney failure (KFRT, estimated glomerular filtration rate <15 mL/min/1.73 m 2 , or death from kidney disease)., Analytical Approach: Because metabolites are often intercorrelated and represent shared pathways, we used a high dimension reduction technique called Netboost to cluster metabolites. Longitudinal associations between clusters of metabolites and KFRT and kidney failure were estimated using a Cox proportional hazards model., Results: Mean age of study participants was 53 years, 61% were African American, and 13% had diabetes. There were 160 KFRT cases and 357 kidney failure cases over a mean of 23 years. The 314 metabolites were grouped in 43 clusters. Four clusters were significantly associated with risk of KFRT and 6 were associated with kidney failure (including 3 shared clusters). The 3 shared clusters suggested potential pathways perturbed early in kidney disease: cluster 5 (15 metabolites involved in alanine, aspartate, and glutamate metabolism as well as 5-oxoproline and several gamma-glutamyl amino acids), cluster 26 (6 metabolites involved in sugar and inositol phosphate metabolism), and cluster 34 (21 metabolites involved in glycerophospholipid metabolism). Several individual metabolites were also significantly associated with both KFRT and kidney failure, including glucose and mannose, which were associated with higher risk of both outcomes, and 5-oxoproline, gamma-glutamyl amino acids, linoleoylglycerophosphocholine, 1,5-anhydroglucitol, which were associated with lower risk of both outcomes., Limitations: Inability to determine if the metabolites cause or are a consequence of changes in kidney function., Conclusions: We identified several clusters of metabolites reproducibly associated with development of KFRT. Future experimental studies are needed to validate our findings as well as continue unraveling metabolic pathways involved in kidney function decline., (© 2022 Published by Elsevier Inc. on behalf of the National Kidney Foundation, Inc.)

Abstract: One of the main pathways for the detoxification of reactive metabolites in the liver involves glutathione conjugation. Metabolic profiling studies have shown paradoxical responses in glutathione-related biochemical pathways. One of these is the increase in 5-oxoproline and ophthalmic acid concentrations with increased dosage of paracetamol. Experimental studies have thus far failed to resolve these paradoxes and the robustness of how these proposed biomarkers correlate with liver glutathione levels has been questioned. To better understand how these biomarkers behave in the glutathione system a kinetic model of this pathway was made. By using metabolic control analysis and by simulating biomarker levels under a variety of conditions, we found that 5-oxoproline and ophthalmic acid concentrations may not only depend on the glutathione but also on the methionine status of the cell. We show that neither of the two potential biomarkers are reliable on their own since they need additional information about the methionine status of the system to relate them uniquely to intracellular glutathione concentration. However, when both biomarkers are measured simultaneously a direct inference of the glutathione concentration can be made, irrespective of the methionine concentration in the system. [Copyright &y& Elsevier]

Pyroglutamic acid or 5-oxoproline is the cyclic lactam of glutamic acid. Its presence in living cells has been reported from archaebacteria to humans, and its occurrence in living cells has been known for over a century. Despite its almost ubiquitous presence, the role of pyroglutamic acid in living cells is poorly understood. Pyroglutamic acid is found as an N-terminal modification in many neuronal peptides and hormones that also include the accumulating peptides in Alzheimer's disease and familial dementia. The modification is also observed in proteins that include many antibodies, some enzymes and structural proteins. The modification in proteins has been shown to contribute to both the structural and activity-related properties of the proteins. Pyroglutamate also exists as a free metabolite in living cells. In several genetic disorders of humans, and in an acetaminophen-induced metabolic disorder, high levels of pyroglutamic acid are secreted in the urine in what is known as 5-oxoprolinuria. The proposed functions of free pyroglutamic acid include its role as an analogue or reservoir of glutamate, as well as other functions unique to it, that includes a possible role in osmoprotection. This short review tries to capture our current understanding of pyroglutamic acid in living cells. [ABSTRACT FROM AUTHOR]

Abstract: 5-Oxoproline (5-OP; pyroglutamate) is an intermediate in the biosynthesis of the endogenous tripeptide glutathione and has been seen to be elevated in the biofluids and tissues of rats following the administration of glutathione-depleting hepatotoxic xenobiotics such as acetaminophen (paracetamol), bromobenzene and ethionine. As 5-OP is a potential biomarker for hepatotoxicity HPLC–MS/MS methods have been developed for its quantification in in vitro cell culture media and rat plasma. For the cell culture media the lower limit of quantification (LLOQ), defined as the lowest concentration on the calibration curve, was 10ng/ml. Minimal carry over was observed for cell culture media between injections (less than 5% at all concentrations examined), precision and accuracy were generally better than 20% for within and between day analyses. For rat plasma a LLOQ of 50ng/ml was obtained. Carry over for plasma was less than 5% for all concentrations, within and between batch accuracy and precision were generally better than 20%. The methods were linear for both sample types from the LLOQ up to 1μg/ml. For samples obtained from rats subjected to chronic administration of the hepatotoxin methapyrilene, concentrations of 5-OP were not observed to increase significantly at any time point compared to controls. 5-OP was also determined in the culture media of human liver epithelial (THLE) cells transfected with cytochrome P450 2E1 (THLE-2E1). Following exposure of THLE-2E1 cells to acetaminophen, large increases in the concentrations of 5-OP were observed, which correlated with reduced cellular glutathione content and with cell toxicity. These results show that LC–MS/MS can be used to perform rapid, sensitive, and quantitative determination of 5-OP in vivo and in vitro and will enable additional investigations into the utility of 5-OP as a biomarker of liver drug-induced liver injury. [Copyright &y& Elsevier]

Nucleophilic substitution of the halogen atom in dimethyl ( S)-4-bromoglutamate followed by removal of the protecting groups and closure of a lactam ring afforded (2 S,4 S)-4-(indolin-1-yl)-5-oxoproline. The indoline fragment was oxidized into the indole fragment to give (2 S,4 S)-4-(indol-1-yl)-5-oxoproline; reduction of the carbonyl groups with BH3 yielded (2 S,4 S)-4-(indol-1-yl)prolines and (2 S,4 S)-2-hydroxymethyl-4-(indol-1-yl)pyrrolidines. Reduction of (2 S,4 S)-4-arylamino-5-oxoprolines with BH3 to the corresponding (2 S,4 S)-4-arylaminoprolines and (2 S,4 S)-4-arylamino-2-hydroxymethylpyrrolidines was studied. [ABSTRACT FROM AUTHOR]

The workup of the emergency patient with a raised anion gap metabolic acidosis includes assessment of the components of "MUDPILES" (methanol; uremia; diabetic ketoacidosis; paraldehyde; isoniazid, iron or inborn errors of metabolism; lactic acid; ethylene glycol; salicylates). This approach is usually sufficient for the majority of cases in the emergency department; however, there are many other etiologies not addressed in this mnemonic. Organic acids including 5-oxoproline (pyroglutamic acid) are rare but important causes of anion gap metabolic acidosis. We present the case of a patient with profound metabolic acidosis with raised anion gap, due to pyroglutamic acid in the setting of malnutrition and chronic ingestion of acetaminophen. [ABSTRACT FROM AUTHOR]

5-Oxoproline accumulates in glutathione synthetase deficiency, an autossomic recessive inherited disorder clinically characterized by hemolytic anemia, metabolic acidosis, and severe neurological symptoms whose mechanisms are poorly known. In the present study we investigated the effects of acute subcutaneous administration of 5-oxoproline to verify whether oxidative stress is elicited by this metabolite in vivo in cerebral cortex and cerebellum of 14-day-old rats. Our results showed that the acute administration of 5-oxoproline is able to promote both lipid and protein oxidation, to impair brain antioxidant defenses, to alter SH/SS ratio and to enhance hydrogen peroxide content, thus promoting oxidative stress in vivo, a mechanism that may be involved in the neuropathology of gluthatione synthetase deficiency. [ABSTRACT FROM AUTHOR]

OXP1/ YKL215c, an uncharacterized ORF of Saccharomyces cerevisiae, encodes a functional ATP-dependent 5-oxoprolinase of 1286 amino acids. The yeast 5-oxoprolinase activity was demonstrated in vivo by utilization of 5-oxoproline as a source of glutamate and OTC, a 5-oxoproline sulfur analogue, as a source of sulfur in cells overexpressing OXP1. In vitro characterization by expression and purification of the recombinant protein in S. cerevisiae revealed that the enzyme exists and functions as a dimer, and has a Km of 159 μM and a Vmax of 3.5 nmol h−1 μg−1 protein. The enzyme was found to be functionally separable in two distinct domains. An ‘actin-like ATPase motif’ could be identified in 5-oxprolinases, and mutation of key residues within this motif led to complete loss in ATPase and 5-oxoprolinase activity of the enzyme. The results are discussed in the light of the previously postulated truncated γ-glutamyl cycle of yeasts. [ABSTRACT FROM AUTHOR]

Cystinosis, an inherited disease caused by a defect in the lysosomal cystine transporter (CTNS), is characterized by renal proximal tubular dysfunction. Adenosine triphosphate (ATP) depletion appears to be a key event in the pathophysiology of the disease, even though the manner in which ATP depletion occurs is still a puzzle. We present a model that explains how a futile cycle that is generated between two ATP-utilizing enzymes of the γ-glutamyl cycle leads to ATP depletion. The enzyme γ-glutamyl cysteine synthetase (γ-GCS), in the absence of cysteine, forms 5- oxoproline (instead of the normal substrate, γ-glutamyl cysteine) and the 5-oxoproline is converted into glutamate by the ATP-dependant enzyme, 5-oxoprolinase. Thus, in cysteine-limiting conditions, glutamate is cycled back into glutamate via 5-oxoproline at the cost of two ATP molecules without production of glutathione and is the cause of the decreased levels of glutathione synthesis, as well as the ATP depletion observed in these cells. The model is also compatible with the differences seen in the human patients and the mouse model of cystinosis, where renal failure is not observed. [ABSTRACT FROM AUTHOR]