Search

Sulfite intoxication is the hallmark of four ultrarare disorders that are caused by impaired sulfite oxidase activity due to genetic defects in the synthesis of the molybdenum cofactor or of the apoenzyme sulfite oxidase. Delays on the diagnosis of these disorders are common and have been caused by their unspecific presentation of acute neonatal encephalopathy with high early mortality, followed by the evolution of dystonic cerebral palsy and also by the lack of easily available and reliable diagnostic tests. There is significant variation in survival and in the quality of symptomatic management of affected children. One of the four disorders, molybdenum cofactor deficiency type A (MoCD‐A) has recently become amenable to causal treatment with synthetic cPMP (fosdenopterin). The evidence base for the rational use of cPMP is very limited. This prompted the formulation of these clinical guidelines to facilitate diagnosis and support the management of patients. The guidelines were developed by experts in diagnosis and treatment of sulfite intoxication disorders. It reflects expert consensus opinion and evidence from a systematic literature search. [ABSTRACT FROM AUTHOR]

Sulfite oxidase is one of five molybdenum-containing enzymes known in eukaryotes where it catalyzes the oxidation of sulfite to sulfate. This review covers the history of sulfite oxidase research starting out with the early years of its discovery as a hepatic mitochondrial enzyme in vertebrates, leading to basic biochemical and structural properties that have inspired research for decades. A personal view on sulfite oxidase in plants, that sulfates are assimilated for their de novo synthesis of cysteine, is presented by Ralf Mendel with numerous unexpected findings and unique properties of this single-cofactor sulfite oxidase localized to peroxisomes. Guenter Schwarz connects his research to sulfite oxidase via its deficiency in humans, demonstrating its unique role amongst all molybdenum enzymes in humans. In essence, in both the plant and animal kingdoms, sulfite oxidase represents an important player in redox regulation, signaling and metabolism, thereby connecting sulfur and nitrogen metabolism in multiple ways. [ABSTRACT FROM AUTHOR]

Background: Molybdenum cofactor deficiency (MoCD) (OMIM# 252150) is an autosomal-recessive disorder caused by mutations in four genes involved in the molybdenum cofactor (MOCO) biosynthesis pathway. Objectives: We reporta milder phenotype in a patient with MOCS1 gene mutation who presented with a Leigh-like presentation. Case report: We present the case of a 10-year-old boy who was symptomatic at the age of 5 months with sudden onset of dyskinesia, nystagmus, and extrapyramidal signs following a febrile illness. Initial biochemical, radiological, and histopathological findings a Leigh syndrome-like phenotype; however, whole-exome sequencing detected compound heterozygous mutations in MOCS1 gene, c.1133 G>C and c.217C>T, confirming an underlying MoCD. This was biochemically supported by low uric acid level of 80 (110-282 mmol/L) and low cystine level of 0 (3-49), and a urine S-sulfocysteine at 116 (0-15) mmol/mol creatinine. The patient was administered methionine- and cystine-free formulas. The patient has remained stable, with residual intellectual, speech, and motor sequelae. Conclusion: This presentation expands the phenotypic variability of late-onset MoCD A and highlights the role of secondary mitochondrial dysfunction in its pathogenesis. [ABSTRACT FROM AUTHOR]

BackgroundMolybdenum cofactor deficiency (MoCD) (OMIM# 252150) is an autosomal-recessive disorder caused by mutations in four genes involved in the molybdenum cofactor (MOCO) biosynthesis pathway.ObjectivesWe report a milder phenotype in a patient with MOCS1 gene mutation who presented with a Leigh-like presentation.Case reportWe present the case of a 10-year-old boy who was symptomatic at the age of 5 months with sudden onset of dyskinesia, nystagmus, and extrapyramidal signs following a febrile illness. Initial biochemical, radiological, and histopathological findings a Leigh syndrome-like phenotype; however, whole-exome sequencing detected compound heterozygous mutations in MOCS1 gene, c.1133 G>C and c.217C>T, confirming an underlying MoCD. This was biochemically supported by low uric acid level of 80 (110–282 mmol/L) and low cystine level of 0 (3–49), and a urine S-sulfocysteine at 116 (0–15) mmol/mol creatinine. The patient was administered methionine- and cystine-free formulas. The patient has remained stable, with residual intellectual, speech, and motor sequelae.ConclusionThis presentation expands the phenotypic variability of late-onset MoCD A and highlights the role of secondary mitochondrial dysfunction in its pathogenesis.

Isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies are genetic diseases biochemically characterized by the toxic accumulation of sulfite in the tissues of patients, including the brain. Neurological dysfunction and brain abnormalities are commonly observed soon after birth, and some patients also have neuropathological alterations in the prenatal period (in utero). Thus, we investigated the effects of sulfite on redox and mitochondrial homeostasis, as well as signaling proteins in the cerebral cortex of rat pups. One-day-old Wistar rats received an intracerebroventricular administration of sulfite (0.5 µmol/g) or vehicle and were euthanized 30 min after injection. Sulfite administration decreased glutathione levels and glutathione S-transferase activity, and increased heme oxygenase-1 content in vivo in the cerebral cortex. Sulfite also reduced the activities of succinate dehydrogenase, creatine kinase, and respiratory chain complexes II and II–III. Furthermore, sulfite increased the cortical content of ERK1/2 and p38. These findings suggest that redox imbalance and bioenergetic impairment induced by sulfite in the brain are pathomechanisms that may contribute to the neuropathology of newborns with ISOD and MoCD. Sulfite disturbs antioxidant defenses, bioenergetics, and signaling pathways in the cerebral cortex of neonatal rats. CII: complex II; CII-III: complex II-III; CK: creatine kinase; GST: glutathione S-transferase; HO-1: heme oxygenase-1; SDH: succinate dehydrogenase; SO32−: sulfite. [ABSTRACT FROM AUTHOR]

Objective To analyze two identical novel MOCS1 gene variant sequences in the same family-with different clinical features, and to provide reliable clinical data for future research on this correlation study. Method The pathogenic gene of the proband′ s family was detected by high-throughput sequencing technology, and clinical features and gene variation sequences of the two patients with type A molybdenum cofactor deficiency from the same family were retrospectively analyzed. Result The proband was a full-term infant with no history of asphyxia, who had difficulty feeding after birth, and had convulsions on the second day. Head MRI showed bilateral basal ganglia hypoxic-ischemic damage and softening lesions. His 5-year-old sibling sister had no abnormal psycho-motor development after birth, but at 10 months, sudden fever and convulsions, feeding difficulties, and progressive overall neurodevelopmental regression were observed. Head MRI also showed hypoxic-ischemic in the basal ganglia. Therefore, the whole exon high-throughput sequencing of 5 members of the family were performed. The pro-band and his affected sister were NM of MOCS1 gene_ 001358530.2, c.1275delA（p.Gly426Aspfs Ter10）homozygous variant, but the parents and another healthy sister all heterozygous variants. This variant site had not been reported. Conclusion The proband and his affected sister have the same MOCS1 gene mutation sequence but different clinical processes. It is speculated that the mild phenotype of the proband may result in the residual function of sulfite oxidase activity. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency (MoCD) is a rare and severe autosomal recessive in-born error of metabolism caused by the mutation in MOCS1, MOCS2, MOCS3 or GEPH genes, with an incidence ranging between 1 in 100,000 and 200,000 live births. The clinical presentation with seizures, lethargy and neurologic deficits reflects the neurotoxicity mediated via sulphite accumulation, and it occurs within the first hours or days after birth, often leading to severe neurodegeneration and the patient's death within days or months. The Imaging of Choice is a brain-specific MRI technique, which is usually performed without contrast and shows typical radiological findings in the early phase, such as diffuse cerebral oedema and infarction affecting the cortex and the basal ganglia and the white matter, as well as in the late phase, such as multicystic encephalomalacia. Our case report represents a novelty in the field, since the patient underwent a contrast-enhanced MRI to exclude a concomitant infectious disease. In the frame of the clinical presentation and laboratory data, we describe the MoCD Imaging findings for MRI morphological and advanced sequences, presenting a new contrast-enhanced MRI pattern characterized by the diffuse and linear leptomeningeal enhancement of brain, cord and spinal roots. The early identification of molybdenum cofactor deficiency is crucial because it may lead to the best multidisciplinary therapy for the patient, which is focused on the prompt and optimal management of the complications. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency type A has successfully been treated in a small number of children with daily intravenous administration of cyclic pyranopterin monophosphate. Pharmacodynamic data for this novel treatment have not been published and alternative dosing intervals have not been explored. We monitored pharmacodynamic biomarkers of sulfite oxidase and xanthine oxidoreductase activity in three patients with MoCD-A for a period of 2 to 9 months after discontinuation of cPMP substitution. We found that the clinical and metabolic effects were sustained for longer than expected, over 7 days at least. Our data implicate a biological half-life of the molybdenum cofactor dependent enzyme activities of approximately 3 days and suggest the possibility that less frequent than once daily dosing intervals could be a safe alternative to current practice. [ABSTRACT FROM AUTHOR]

Sulfite oxidase is one of five molybdenum-containing enzymes known in eukaryotes where it catalyzes the oxidation of sulfite to sulfate. This review covers the history of sulfite oxidase research starting out with the early years of its discovery as a hepatic mitochondrial enzyme in vertebrates, leading to basic biochemical and structural properties that have inspired research for decades. A personal view on sulfite oxidase in plants, that sulfates are assimilated for their de novo synthesis of cysteine, is presented by Ralf Mendel with numerous unexpected findings and unique properties of this single-cofactor sulfite oxidase localized to peroxisomes. Guenter Schwarz connects his research to sulfite oxidase via its deficiency in humans, demonstrating its unique role amongst all molybdenum enzymes in humans. In essence, in both the plant and animal kingdoms, sulfite oxidase represents an important player in redox regulation, signaling and metabolism, thereby connecting sulfur and nitrogen metabolism in multiple ways.

Molybdenum cofactor (Moco) deficiency (MoCD) is characterized by neonatal-onset myoclonic epileptic encephalopathy and dystonia with cerebral MRI changes similar to hypoxic–ischemic lesions. The molecular cause of the disease is the loss of sulfite oxidase (SOX) activity, one of four Moco-dependent enzymes in men. Accumulating toxic sulfite causes a secondary increase of metabolites such as S-sulfocysteine and thiosulfate as well as a decrease in cysteine and its oxidized form, cystine. Moco is synthesized by a three-step biosynthetic pathway that involves the gene products of MOCS1, MOCS2, MOCS3, and GPHN. Depending on which synthetic step is impaired, MoCD is classified as type A, B, or C. This distinction is relevant for patient management because the metabolic block in MoCD type A can be circumvented by administering cyclic pyranopterin monophosphate (cPMP). Substitution therapy with cPMP is highly effective in reducing sulfite toxicity and restoring biochemical homeostasis, while the clinical outcome critically depends on the degree of brain injury prior to the start of treatment. In the absence of a specific treatment for MoCD type B/C and SOX deficiency, we summarize recent progress in our understanding of the underlying metabolic changes in cysteine homeostasis and propose novel therapeutic interventions to circumvent those pathological changes. [ABSTRACT FROM AUTHOR]

Objective: We investigated neonatal seizures in three probands admitted to the neonatal intensive care units and their affected family members., Methods: Whole exome sequencing (WES) was performed along with confirmation by Sanger sequencing and segregation analysis. Copy number variant (CNV) analysis was also conducted. Neuroimaging, electroencephalography, and metabolic analysis revealed clinical phenotypes., Results: Bi-allelic variants c.1025T>C and c.1150G>A in MOCS1 were found in twin girls with molybdenum cofactor deficiency. The c.1025T>C variant was novel. A c.877C>T variant in KCNQ2 co-segregated with seizures in a family. A de novo 6.25 Mb duplication on 2q24.3 encompassing SCN1A, SCN2A, and SCN3A was identified in a proband who demonstrated normal development without seizures on follow-up., Significance: WES facilitated the molecular diagnosis of neonatal seizures in the study participants. Variants in the KCNQ2 and MOCS1 genes were classified as likely pathogenic based on our findings. The individual with a duplication of the sodium channel gene cluster on 2q24.3 exhibited additional phenotypes. Our investigation expanded the genotype-phenotype spectrum., (© 2024 International League Against Epilepsy.)

We report the first, and so far, only index patient with neonatal onset MoCD type A who was diagnosed and treated early enough with cPMP to avoid severe brain injury and disability. The child presented with hypoglycemia at the age of 10 h and was diagnosed because of the incidental finding of severely decreased L-cystine in plasma. Due to a high level of awareness and excellent co-operation between metabolic laboratory and clinical services, cPMP substitution could be initiated before severe encephalopathy set in, and the child subsequently had a normal motor development. The child has been continued on daily substitution with cPMP until today (age 7 years) and has shown a satisfying long-term developmental outcome. Long-term follow-up, however, revealed significant communication difficulties and cognitive abilities in the range of mild to moderate learning disability. The severity of the metabolic disease was confirmed by the extent of biochemical abnormalities and further functional characterisation of the underlying genetic variants. This case provides further evidence that cPMP substitution does significantly alter the disease course when applied early enough. Postnatal treatment in this case was not sufficient to enable an entirely normal cognitive development, despite sustained complete normalization of the biochemical abnormalities., Competing Interests: Declaration of competing interest Bernd C Schwahn reports an unconditional educational grant to MFT in support of a scientific meeting and a honorarium for an advisory board meeting from Origin Biosciences Inc., and was principal investigator for clinical trials sponsored by Alexion Inc. and Origin Biosciences, Inc. Charles Turner is a Director and minority shareholder of SpOtOn Clinical Diagnostics who supplied reagents for some of the assays. Günter Schwarz reports conflicts for member of advisory board or similar committee with Origin Biosciences, consulting or speaker fee from Sentynl, holding a patent with Sentynl, and founder and CEO of Colbourne Pharmaceuticals GmbH involved in the early stages of development of cPMP therapy. Claire Hart, Louisa-Ann Smith, Anthony Hart, Monica Arenas-Hernandez, Alistair Horman, Stewart Rust, Jose-Angel Santamaria-Araujo and Simon J Mayr report no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: To report a rare case of Molybdenum Cofactor Deficiency with novel ocular manifestations. Observations: This is a case study of a 6-year-old boy who initially presented with conjunctival hyperemia and ocular pain of the left eye. Medical history revealed refractory convulsion, global developmental delay, microcephaly, feeding difficulties, aphasia, and spastic quadriplegia, as well as pathogenic MOCS2 mutations, indicating the diagnosis of molybdenum cofactor deficiency (MoCD). This case report highlights detailed ocular manifestations of late-onset MoCD-B, ectopia lentis of bilateral eyes, spherophakia, hyperemia, secondary glaucoma, cyclodialysis, and retinal detachment of the left eye, which will help further understanding of MoCD. Conclusions and importance: MoCD as a rare genetic disease is tend to be easily neglected. The ophthalmic examination could provide important evidence for early diagnosis.

Molybdenum cofactor deficiency (MoCD) is a rare and severe autosomal recessive in-born error of metabolism caused by the mutation in MOCS1, MOCS2, MOCS3 or GEPH genes, with an incidence ranging between 1 in 100,000 and 200,000 live births. The clinical presentation with seizures, lethargy and neurologic deficits reflects the neurotoxicity mediated via sulphite accumulation, and it occurs within the first hours or days after birth, often leading to severe neurodegeneration and the patient’s death within days or months. The Imaging of Choice is a brain-specific MRI technique, which is usually performed without contrast and shows typical radiological findings in the early phase, such as diffuse cerebral oedema and infarction affecting the cortex and the basal ganglia and the white matter, as well as in the late phase, such as multicystic encephalomalacia. Our case report represents a novelty in the field, since the patient underwent a contrast-enhanced MRI to exclude a concomitant infectious disease. In the frame of the clinical presentation and laboratory data, we describe the MoCD Imaging findings for MRI morphological and advanced sequences, presenting a new contrast-enhanced MRI pattern characterized by the diffuse and linear leptomeningeal enhancement of brain, cord and spinal roots. The early identification of molybdenum cofactor deficiency is crucial because it may lead to the best multidisciplinary therapy for the patient, which is focused on the prompt and optimal management of the complications.

Molybdenum cofactor deficiency (MoCD) is a rare autosomal recessive metabolic disease with deficiency of molibden cofactor and associated enzymes aldehyde oxidase, xanthine oxidase and sulfite oxidase. The most common type is A, which is caused by mutation in MOCS1 gene. Typical clinical picture presents in the newborn period with intractable seizures, abnormal muscle tone, altered mental status, feeding and respiratory disturbances, autonomic disfunction, so that resembles hypoxic ischaemic encephalopathy. Most patients die in the first weeks. If they survive, there are severe neurological consequences like tetraparesis with spasticity/ dystonia, epilepsy, severe developmental delay, and progressive microcephaly. Since February 2021 year Fosdenopterin has been approved by the FDA for the treatment of MoCD type A. When it starts presymptomatically or in the beginning of the disease the prognosis becomes better with reducing either the risk of mortality or the brain damage and the severety of neurologic consequences. We report an infant with genetically proved molybdenum cofactor deficiency, which mimic clinically and by images hypoxic ischaemic encephalopathy, followed by cerebral palsy and developmental delay . At the age of 1year 10 months death occurred. The route to fast diagnosis excluding possible wrong diagnoses is discussed. Neonatologists, pediatricians and pediatric neurologists should be aware of this disease not to miss the diagnosis. It could help for propper treatment and for prenatal diagnosis in future pregnancies. [ABSTRACT FROM AUTHOR]

Background To describe the genotype-phenotype dissociation in two Taiwanese patients with molybdenum cofactor deficiency (MoCoD) caused by MOCS2 gene mutations. Patient Description Patient 1 exhibited early-onset neurological symptoms soon after birth, followed by subsequent myoclonic seizures and movement disorder. The brain magnetic resonance imaging (MRI) showed diffuse brain injury with cystic encephalomalacia along with bilateral globus pallidi involvement, hypoplasia of corpus callosum, and cerebellar atrophy. Patient 2 had a mild phenotype with prominent movement disorder after intercurrent illness, and the brain MRI showed selective injury of the bilateral globus pallidi and the cerebellum. Both patients had markedly low levels of plasma uric acid and harbored the same MOCS2 homozygous c.16C > T mutation. Patient 1 showed chronic regression of developmental milestones and died of respiratory failure at the age of 8 years, whereas patient 2 demonstrated improvement in motor function. Conclusion Genotype-phenotype dissociation could be noted in patients with MoCoD due to MOCS2 mutation. Patients with neonatal seizures, developmental delay, movement disorder, and motor regression after an illness, as well as focal or bilateral involvement of the globus pallidi on the neuroimages, should undergo biochemical testing of plasma uric acid. A pronounced plasma uric acid level is a good indicator of MoCoD. Early diagnosis can allow early provision of adequate genetic counseling. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency (MoCD) includes three ultrarare autosomal recessive inborn errors of metabolism (MoCD type A [MoCD‐A], MoCD‐B, and MoCD‐C) that cause sulfite intoxication disorders. This natural history study analyzed retrospective data for 58 living or deceased patients (MoCD‐A, n = 41; MoCD‐B, n = 17). MoCD genotype, survival, neuroimaging, and medical history were assessed retrospectively. Prospective biomarker data were collected for 21 living MoCD patients. The primary endpoint was survival to 1 year of age in MoCD‐A patients. Of the 58 MoCD patients, 49 (MoCD‐A, n = 36; MoCD‐B, n = 13) had first presenting symptoms by Day 28 (neonatal onset; median: 2 and 4 days, respectively). One‐year survival rates were 77.4% (overall), 71.8% (neonatal onset MoCD‐A), and 76.9% (neonatal onset MoCD‐B); median ages at death were 2.4, 2.4, and 2.2 years, respectively. The most common presenting symptoms in the overall population were seizures (60.3%) and feeding difficulties (53.4%). Sequelae included profound developmental delay, truncal hypotonia, limb hypertonia that evolved to spastic quadriplegia or diplegia, dysmorphic features, and acquired microcephaly. In MoCD‐A and MoCD‐B, plasma and urinary xanthine and S‐sulfocysteine concentrations were high; urate remained below the normal reference range. MOCS1 mutation homozygosity was common. Six novel mutations were identified. MoCD is a severe neurodegenerative disorder that often manifests during the neonatal period with intractable seizures and feeding difficulties, with rapidly progressive significant neurologic disabilities and high 1‐year mortality rates. Delineation of MoCD natural history supports evaluations of emerging replacement therapy with cPMP for MoCD‐A, which may modify disease course for affected individuals. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor (Moco) deficiency (MoCD) is characterized by neonatal-onset myoclonic epileptic encephalopathy and dystonia with cerebral MRI changes similar to hypoxic–ischemic lesions. The molecular cause of the disease is the loss of sulfite oxidase (SOX) activity, one of four Moco-dependent enzymes in men. Accumulating toxic sulfite causes a secondary increase of metabolites such as S-sulfocysteine and thiosulfate as well as a decrease in cysteine and its oxidized form, cystine. Moco is synthesized by a three-step biosynthetic pathway that involves the gene products of MOCS1, MOCS2, MOCS3, and GPHN. Depending on which synthetic step is impaired, MoCD is classified as type A, B, or C. This distinction is relevant for patient management because the metabolic block in MoCD type A can be circumvented by administering cyclic pyranopterin monophosphate (cPMP). Substitution therapy with cPMP is highly effective in reducing sulfite toxicity and restoring biochemical homeostasis, while the clinical outcome critically depends on the degree of brain injury prior to the start of treatment. In the absence of a specific treatment for MoCD type B/C and SOX deficiency, we summarize recent progress in our understanding of the underlying metabolic changes in cysteine homeostasis and propose novel therapeutic interventions to circumvent those pathological changes.

The article presents a clinical study of an infant with rare inherited metabolism disorder – molybdenum cofactor deficiency, for the first time in Russian literature. The onset of disorder – in early neonatal period with a suppression syndrome and myoclonic seizures combined with a burstsuppression electroencephalographic patterns, followed by a reveal of psychomotor delay. Сraniofacial dystrophies were present, including craniostenosis and microcephaly. Somatic status was characterized by hepatolienomegaly, dysmetabolic changes of kidneys’ parenchyma (suggested by ultrasound) and crystalluria. Neuroimaging data were contradictory. Neurosonography results allowed diagnosing concomitant inborn brain development defect: true porencephalia of large hemispheres. However, brain magnetic resonance imaging revealed a picture of diffuse leukomalacia with pseudocyst formation, which were considered a consequence of perinatal brain damage. Magnetic resonance imaging revealed a picture of diffuse leukomalacia with pseudocyst formation, which were considered a consequence of perinatal brain damage. Differential diagnosis was held between the early infantile epileptic encephalopathy (Ohtahara syndrome) and early myoclonic encephalopathy (Aicardi syndrome). However, etiology of the disease remained unclear. To eliminate inherited metabolic disease accompanied by epilepsy, Inherited Epilepsy Panel DNA sequencing was used. The results showed a homozygotic mutation on the exon 6 of MOCS2 gene, leading to deletion of amino acid in position 158 of the protein, which was described before in patients with molybdenum cofactor deficiency (OMIM: 252160).

Background: The molybdenum cofactor (Moco) deficiency in humans results in the inactivity of molybdenum-dependent enzymes and is caused by pathogenic variants in MOCS1 (Molybdenum cofactor synthesis 1), MOCS2 (Molybdenum cofactor synthesis 2), and GPHN (Gephyrin). These genes along with MOCS3 (Molybdenum cofactor synthesis 3) are involved in Moco biosynthesis and providing cofactors to Moco-dependent enzymes. Until now, there was no study to confirm that MOCS3 is a causative gene of Moco deficiency.Methods: Detailed clinical information was collected in the pedigree. The Whole-exome sequencing (WES) accompanied with Sanger sequencing validation were performed.Results: We described the clinical presentations of an infant, born to a non-consanguineous healthy family, diagnosed as having MOCS3 variants caused Moco deficiency and showing typical features of Moco deficiency including severe neurologic symptoms and cystic encephalomalacia in the brain MRI, resulting in neonatal death. Compound heterozygous variants in the MOCS3 gene were identified by WES. Positive sulfite and decreased levels of uric acid in plasma and urine were detected.Conclusion: To our knowledge, this is the first case of MOCS3 variants causing Moco deficiency. Our study may contribute to genetic diagnosis of Moco deficiency and future genetic counseling.

Background: The molybdenum cofactor (Moco) deficiency in humans results in the inactivity of molybdenum-dependent enzymes and is caused by pathogenic variants in MOCS1 (Molybdenum cofactor synthesis 1), MOCS2 (Molybdenum cofactor synthesis 2), and GPHN (Gephyrin). These genes along with MOCS3 (Molybdenum cofactor synthesis 3) are involved in Moco biosynthesis and providing cofactors to Moco-dependent enzymes. Until now, there was no study to confirm that MOCS3 is a causative gene of Moco deficiency. Methods: Detailed clinical information was collected in the pedigree. The Whole-exome sequencing (WES) accompanied with Sanger sequencing validation were performed. Results: We described the clinical presentations of an infant, born to a non-consanguineous healthy family, diagnosed as having MOCS3 variants caused Moco deficiency and showing typical features of Moco deficiency including severe neurologic symptoms and cystic encephalomalacia in the brain MRI, resulting in neonatal death. Compound heterozygous variants in the MOCS3 gene were identified by WES. Positive sulfite and decreased levels of uric acid in plasma and urine were detected. Conclusion: To our knowledge, this is the first case of MOCS3 variants causing Moco deficiency. Our study may contribute to genetic diagnosis of Moco deficiency and future genetic counseling. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Contemporary Pediatrics is the property of Xiangya Medical Periodical Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Molybdenum cofactor deficiency (MoCD) is an autosomal recessive disorder belonging to the large family of inborn errors in metabolism. Patients typically present with encephalopathy and seizures early after birth and develop severe neurodegeneration within the first few weeks of life. The main pathomechanism underlying MoCD is the loss of function of sulfite oxidase (SO), a molybdenum cofactor (Moco) dependent enzyme located in mitochondrial intermembrane space. SO catalyzes the oxidation of sulfite (SO32–) to sulfate (SO42–) in the terminal reaction of cysteine catabolism, and in the absence of its activity, sulfurous compounds such as SO32–, S-sulfocysteine, and thiosulfate accumulate in patients. Despite growing evidence that these compounds affect neuronal and mitochondrial function, the molecular basis of neuronal dysfunction and cell death in MoCD is still poorly understood. Here we show that mitochondria are severely affected by the loss of SO activity. SO-deficient mouse embryonic fibroblasts display reduced growth rates and impaired ATP production when cultured in galactose, which is an indicator of mitochondrial dysfunction. We also found that mitochondria in SO-deficient cells form a highly interconnected network compared to controls while displaying a slight decrease in motility and unchanged mitochondrial mass. Moreover, we show that the mitochondrial network is directly influenced by SO32–, as a moderate elevation of SO32– lead to the formation of an interconnected mitochondrial network, while high SO32– levels induced fragmentation. Finally, we found a highly interconnected mitochondrial network in MoCD patient-derived fibroblasts, similar to our findings in mouse-derived fibroblasts. We therefore conclude that altered mitochondrial dynamics are an important contributor to the disease phenotype and suggest that MoCD should be included among the mitochondrial disorders.

Molybdenum cofactor deficiency (MoCD) is an autosomal recessive disorder belonging to the large family of inborn errors in metabolism. Patients typically present with encephalopathy and seizures early after birth and develop severe neurodegeneration within the first few weeks of life. The main pathomechanism underlying MoCD is the loss of function of sulfite oxidase (SO), a molybdenum cofactor (Moco) dependent enzyme located in mitochondrial intermembrane space. SO catalyzes the oxidation of sulfite (SO32–) to sulfate (SO42–) in the terminal reaction of cysteine catabolism, and in the absence of its activity, sulfurous compounds such as SO32–, S-sulfocysteine, and thiosulfate accumulate in patients. Despite growing evidence that these compounds affect neuronal and mitochondrial function, the molecular basis of neuronal dysfunction and cell death in MoCD is still poorly understood. Here we show that mitochondria are severely affected by the loss of SO activity. SO-deficient mouse embryonic fibroblasts display reduced growth rates and impaired ATP production when cultured in galactose, which is an indicator of mitochondrial dysfunction. We also found that mitochondria in SO-deficient cells form a highly interconnected network compared to controls while displaying a slight decrease in motility and unchanged mitochondrial mass. Moreover, we show that the mitochondrial network is directly influenced by SO32–, as a moderate elevation of SO32– lead to the formation of an interconnected mitochondrial network, while high SO32– levels induced fragmentation. Finally, we found a highly interconnected mitochondrial network in MoCD patient-derived fibroblasts, similar to our findings in mouse-derived fibroblasts. We therefore conclude that altered mitochondrial dynamics are an important contributor to the disease phenotype and suggest that MoCD should be included among the mitochondrial disorders. [ABSTRACT FROM AUTHOR]

Isolated sulfite oxidase deficiency (ISOD) is a rare autosomal recessively inherited inborn error of metabolism, caused by mutation in SUOX gene. ISOD has two kind of presentation; early and late-onset. The late-onset form is extremely rare and only 10 cases have been reported. We report two new cases of late-onset ISOD with biochemical and genetic confirmation. We did a review of the previously published cases of late-onset ISOD. Together with the presented two cases, 12 cases were available for analysis. The median age at symptom onset and at diagnosis was 8.5 and 23 months respectively. Almost all children had acute regression of milestones followed by slow recovery. The common presenting signs and symptoms were movement disorders, seizures, ectopia lentis and hypertonia. Five children had antecedent events. Trivial trauma precipitating the metabolic crisis was unique to the two cases we report. The most common MRI feature was globus pallidi changes followed by cerebellar white matter changes, vermian hypoplasia and thinned out corpus callosum. Diffusion weighted sequence was performed in 3 children and all had diffusion restriction in the affected area. Trivial trauma can precipitate metabolic crisis in late-onset ISOD. Low plasma homocysteine and involvement of globus pallidi with diffusion restriction on the MRI are important diagnostic clues. Early diagnosis and intervention with special diet may be effective in preventing long term neurodisability. [ABSTRACT FROM AUTHOR]

Abstract Background Molybdenum cofactor deficiency (MoCD) is a rare autosomal‐recessive disorder that results in the combined deficiency of molybdenum‐dependent enzymes. Four different genes are involved in Molybdenum cofactor biosynthesis: MOCS1, MOCS2, MOCS3, and GEPH. The classical form manifests in the neonatal period with severe encephalopathy, including intractable seizures, MRI changes that resemble hypoxic‐ischemic injury, microcephaly, and early death. To date, an atypical phenotype with late‐onset has been reported in the literature in 13 patients. Methods We describe a late‐onset and a relatively mild phenotype in a patient with MOCS2 homozygous mutation. Results Pyramidal and extrapyramidal signs are recognized in those patients, often exacerbated by intercurrent illness. Expressive language is usually compromised. Neurological deterioration is possible even in adulthood, probably due to accumulation of sulfite with time. Conclusion Sulfite inhibition of mitochondrial metabolism could be responsible for the ischemic lesions described in patients with MoCD or alternatively could predispose the brain to suffer an ischemic damage through the action of other insults, for instance intercurrent illness. It is possible that sulfite accumulation together with other external triggers, can lead to neurological deterioration even in adulthood. The role of other factors involved in clinical expression should be investigated to establish the reason for phenotypic variability in patients with the same mutation.

Molybdenum cofactor deficiency is an autosomal, recessively inherited metabolic disorder, which, in the absence of an effective therapy, leads to early childhood death due to neurological deterioration. In type A of the disease, cyclic pyranopterin monophosphate (cPMP) is missing, the first intermediate in the biosynthesis of the cofactor, and a biochemical substitution therapy using cPMP has been developed. A comparable approach for type B of the disease with a defect in the second step of the synthesis, formation of molybdopterin, so far has been hampered by the extreme instability of the corresponding metabolites. To explore avenues for a successful and safe gene therapy, knock-in mouse models were created carrying the mutations c.88C>T (p.Q30X) and c.726_727delAA, which are also found in human patients. Recombinant adeno-associated viruses (rAAVs) were constructed and used for postnatal intrahepatic injections of MoCo-deficient mice in a proof-of-concept approach. Singular administration of an appropriate virus dose in 60 animals prevented the otherwise devastating phenotype to a variable extent. While untreated mice did not survive for more than 2 weeks, some of the treated mice grew up to adulthood in both sexes. [ABSTRACT FROM AUTHOR]

Summary: In cereal crops, ABA deficiency during seed maturation phase causes pre‐harvest sprouting (PHS), and molybdenum cofactor (MoCo) is required for ABA biosynthesis.Here, two rice PHS mutants F254 and F5‐1 were characterized. In addition to the PHS, these mutants showed pleiotropic phenotypes such as twisting and slender leaves, and then died when the seedling developed to four or five leaves. Map‐based cloning showed that OsCNX6 and OsCNX1 encoding homologs of MoaE and MoeA were responsible for F254 and F5‐1 mutants, respectively. Genetic complementation indicated that OsCNX6 not only rescued the PHS and seedling lethal phenotype of the cnx6 mutant, but also recovered the MoCo‐dependent enzyme activities such as xanthine dehydrogenase (XDH), aldehyde oxidase (AO), nitrate reductase (NR) and sulfite oxidase (SO).Expression pattern showed that OsCNX6 was richly expressed in seed during embryo maturation by quantitative reverse transcriptase PCR and RNA in situ hybridization. Furthermore, the OsCNX6 overexpression plants can significantly enhance the MoCo‐dependent enzyme activities, and improved the osmotic and salt stress tolerance without unfavorable phenotypes.Collectively, these data indicated that OsCNX6 participated in MoCo biosynthesis, and is essential for rice development, especially for seed dormancy and germination, and OsCNX6 could be an effective target for improving abiotic stress tolerance in rice. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency (MoCD) is a rare autosomal recessive metabolic disease with severe neurological symptoms. Most disease-causing mutations are found in the MOCS1 gene, corresponding to MoCD type A (MoCD-A). There have been few reports describing the long-term detailed neurological features with MoCD-A because most patients do not survive childhood. We describe the clinical, radiologic, biochemical, and genetic data of two patients (female siblings aged 26 and 22 years) with MoCD-A. Both patients presented with feeding difficulties, neurological deterioration, and persistent generalized muscle contraction which can be easily confused with status dystonicus. Biochemical tests revealed low serum uric acid, elevated urinary sulfocysteine, and xanthine. Brain magnetic resonance imaging (MRI) revealed distinctive abnormalities in the bilateral caudate nucleus, putamen, globus pallidus, and cerebral white matter adjacent to the cortex. The thalamus was relatively unaffected. Genetic testing identified a novel homozygous variant in the MOCS1 gene (c.949C > T p.Arg317Cys). Biochemical results supported the hypothesis that this genetic variant is a pathological mutation. When there are symptoms of persistent generalized muscle contraction and characteristic MRI findings, MoCD should be considered as a differential diagnosis. [ABSTRACT FROM AUTHOR]

Sulfite oxidase (SO) deficiency, an inherited disease that causes severe neonatal neurological problems and early death, arises from defects in the biosynthesis of the molybdenum cofactor (Moco) (general sulfite oxidase deficiency) or from inborn errors in the SUOX gene for SO (isolated sulfite oxidase deficiency, ISOD). The X-ray structure of the highly homologous homonuclear dimeric chicken sulfite oxidase (cSO) provides a template for locating ISOD mutation sites in human sulfite oxidase (hSO). Catalysis occurs within an individual subunit of hSO, but mutations that disrupt the hSO dimer are pathological. The catalytic cycle of SO involves five metal oxidation states (MoVI, MoV, MoIV, FeIII, FeII), two intramolecular electron transfer (IET) steps, and couples a two-electron oxygen atom transfer reaction at the Mo center with two one-electron transfers from the integral b -type heme to exogenous cytochrome c , the physiological oxidant. Several ISOD examples are analyzed using steady-state, stopped-flow, and laser flash photolysis kinetics and physical measurements of recombinant variants of hSO and native cSO. In the structure of cSO, Mo ... Fe = 32 Å, much too long for efficient IET through the protein. Interdomain motion that brings the Mo and heme centers closer together to facilitate IET is supported indirectly by decreasing the length of the interdomain tether, by changes in the charges of surface residues of the Mo and heme domains, as well as by preliminary molecular dynamics calculations. However, direct dynamic measurements of interdomain motion are in their infancy. A flexible tether links the molybdenum cofactor (Moco) and heme domains of sulfite oxidase (SO). Catalysis involves: two-electron reduction of MoVI; intramolecular electron transfer (IET 1, MoV/FeII); intermolecular transfer to oxidized cytochrome c (MoV/FeIII); intramolecular electron transfer (IET 2, MoVI/FeII); a second electron transfer to oxidized cytochrome c (MoVI/FeIII). [Display omitted] • Mutations that disrupt the sulfite oxidase dimer are catalytically inactive. • Catalytic oxidation of sulfite occurs within one subunit of the sulfite oxidase dimer. • Sulfite oxidase catalysis involves two intramolecular electron transfer (IET) steps. • Interdomain tether length alters catalysis and intramolecular electron transfer (IET). • Chicken sulfite oxidase (cSO) is a template for human sulfite oxidase (hSO) mutations. [ABSTRACT FROM AUTHOR]

The article presents a case study related to patient suffering from renal stones in an infant with microcephaly and spastic quadriparesis. Topics include the xanthine dehydrogenase and aldehyde oxidase has involved in metabolism of certain drugs, the molybdenum cofactor deficiency (HX type III) can also cause xanthine renal stones, and its incidence being much rarer in infants and children compared with the other two types, and the patients being prone to recurrent urolithiasis.

Background The aim of our study was to identify the genetic background of thiopurine-induced toxicity in a patient with a wild-type thiopurine methyltransferase genotype and activity. A 38-year-old Caucasian woman presented with cutaneous necrotizing vasculitis pancytopenia one month after starting azathioprine therapy. Methods During a routine biochemical follow-up of the patient, undetectable serum uric acid (<10 μl) was observed. A high performance liquid chromatography analysis of urinary purines revealed increased levels of xanthine (137 mmol/mol creatinine). The suspected diagnosis of hereditary xanthinuria, a rare autosomal recessive disorder of the last two steps of purine metabolism, was confirmed by sequence analysis. Results An analysis of XDH/XO and AOX1 revealed common polymorphisms, while analysis of the MOCOS gene identified a rare homozygous variant c.362C > T. Dysfunction of this variant was confirmed by significantly decreased xanthine dehydrogenase/oxidase activity in the patient's plasma (<2% of control mean activity). Conclusions We present a biochemical, enzymatic, and molecular genetic case study suggesting an important association between a hitherto undescribed dysfunction variant in the MOCOS gene and thiopurine-induced toxicity. The identified variant c.362C > T results in slower thiopurine metabolism caused by inhibition of 6-mercaptopurine oxidation (catabolism) to 6-thioxanthine and 6-thiouric acid, which increases the formation of the nucleotide 6-thioguanine, which is toxic. This is the first clinical case to identify the crucial role of the MOCOS gene in thiopurine intolerance and confirm the impact of genetic variability of purine enzymes on different therapeutic outcomes in patients undergoing thiopurine treatment. [ABSTRACT FROM AUTHOR]

Translucency of the larval integument in Bombyx mori is caused by a lack of uric acid in the epidermis. Hime'nichi translucent ( ohi ) is a unique mutation causing intermediate translucency of the larval integument and male-specific flaccid paralysis. To determine the gene associated with the ohi mutation, the ohi locus was mapped to a 400-kb region containing 29 predicted genes. Among the genes in this region, we focused on Bombyx homolog of mammalian Gephyrin ( BmGphn ), which regulates molybdenum cofactor (MoCo) biosynthesis, because MoCo is indispensable for the activity of xanthine dehydrogenase (XDH), a key enzyme in uric acid biosynthesis. The translucent integument of ohi larvae turned opaque after injection of bovine xanthine oxidase, which is a mammalian equivalent to XDH, indicating that XDH activity is defective in ohi larvae. RT-PCR and sequencing analysis showed that (i) in ohi larvae, expression of the BmGphn gene was repressed in the fat body where uric acid is synthesized, and (ii) there was no amino acid substitution in the ohi mutant allele. Finally, we obtained BmGphn knockout alleles (hereafter denoted as BmGphn Δ ) by using CRISPR/Cas9. The resulting ohi / BmGphn Δ larvae had translucent integuments, demonstrating that BmGphn is the gene responsible for the ohi phenotype. Our results show that repressed expression of BmGphn is a causative factor for the defective MoCo biosynthesis and XDH activity observed in ohi larvae. Interestingly, all male BmGphn Δ homozygotes died before pupation and showed a flaccid paralysis phenotype. The genetic and physiological mechanisms underlying this flaccid paralysis phenotype are also discussed. [ABSTRACT FROM AUTHOR]

Summary: The nitrogen, sulfur and carbon cycles all rely on critical microbial transformations that are carried out by enzymes that require molybdenum (Mo) as a cofactor. Despite Mo importance in these biogeochemical cycles, little information exists about microbial Mo utilization in extreme environments where, due to geochemical conditions, bioavailable Mo may be limited. Using metagenomic data from nine hot springs in Tengchong, Yunnan Province, China, which range in temperature from 42°C to 96°C and pH from 2.3 to 9, the effects of pH, temperature and spring geochemistry on the abundance and taxonomic affiliation of genes related to Mo were studied. Dissolved Mo was only detected at sites with circumneutral pH. However, processes and organisms that require Mo were detected at all sites across all temperature and pH gradients. All sites contained xanthine dehydrogenase, formate dehydrogenase, carbon‐monoxide dehydrogenase, nitrate reductase, sulfite oxidase and methionine‐sulfoxide reductase despite different community compositions. This suggests that different microbial communities, resulting from different physicochemical conditions, may be performing similar metabolic functions. Furthermore, the abundance and taxonomic diversity of Mo‐related annotations increased with higher concentrations of Mo. This study shows that despite geochemical conditions that can limit Mo bioavailability, microbes require Mo for a variety of processes. [ABSTRACT FROM AUTHOR]

The human mitochondrial amidoxime reducing component (hmARC) is a molybdenum cofactor‐dependent enzyme that is involved in the reduction of a diverse range of N‐hydroxylated compounds of either physiological or xenobiotic origin. In this study, the use of a fusion‐protein approach with T4 lysozyme (T4L) to determine the structure of this hitherto noncrystallizable enzyme by X‐ray crystallography is described. A set of four different hmARC‐T4L fusion proteins were designed. Two of them contained either an N‐terminal or a C‐terminal T4L moiety fused to hmARC, while the other two contained T4L as an internal fusion partner tethered to the hmARC enzyme between two predicted secondary‐structure elements. One of these internal fusion constructs could be expressed and crystallized successfully. The hmARC‐T4L crystals diffracted to 1.7 Å resolution using synchrotron radiation and belonged to space group P212121 with one molecule in the asymmetric unit. Initial attempts to solve the structure by molecular replacement using T4L did not result in electron‐density distributions that were sufficient for model building and interpretation of the hmARC moiety. However, this study emphasizes the utility of the T4L fusion‐protein approach, which can be used for the crystallization and structure determination of membrane‐bound proteins as well as soluble proteins. [ABSTRACT FROM AUTHOR]

Molybdenum cofactor deficiency (MoCD) is an autosomal recessive inborn error of metabolism characterized by neurodegeneration and death in early childhood. The rapid and progressive neurodegeneration in MoCD presents a major clinical challenge and may relate to the poor understanding of the molecular mechanisms involved. Recently, we reported that treating patients with cyclic pyranopterin monophosphate (cPMP) is a successful therapy for a subset of infants with MoCD and prevents irreversible brain damage. Here, we studied S-sulfocysteine (SSC), a structural analog of glutamate that accumulates in the plasma and urine of patients with MoCD, and demonstrated that it acts as an N-methyl D-aspartate receptor (NMDA-R) agonist, leading to calcium influx and downstream cell signaling events and neurotoxicity. SSC treatment activated the protease calpain, and calpain-dependent degradation of the inhibitory synaptic protein gephyrin subsequently exacerbated SSC-mediated excitotoxicity and promoted loss of GABAergic synapses. Pharmacological blockade of NMDA-R, calcium influx, or calpain activity abolished SSC and glutamate neurotoxicity in primary murine neurons. Finally, the NMDA-R antagonist memantine was protective against the manifestation of symptoms in a tungstate-induced MoCD mouse model. These findings demonstrate that SSC drives excitotoxic neurodegeneration in MoCD and introduce NMDA-R antagonists as potential therapeutics for this fatal disease. [ABSTRACT FROM AUTHOR]

Sulfite oxidase deficiency (SOD) and related disorders, especially molybdenum cofactor deficiency (MoCD), are a group of rare and severe neurometabolic disorders caused by gene mutations that affect the sulfur-containing amino acid catabolic pathway. These disorders are characterized by distinctive neuroimaging features such as diffuse cerebral atrophy, multicystic encephalomalacia, and ventriculomegaly in early infancy. These features are essential for early diagnosis and treatment. Moreover, the genetics of these disorders are complex but have been increasingly elucidated in the era of molecular medicine. Therefore, we reviewed 28 articles (published from January 1967 until October 2021) on SOD and MoCD, focusing on their neuroimaging and genetic aspects. We highlighted the differences between SOD and MoCD and other conditions that may mimic them, such as common neonatal hypoxic-ischemic encephalopathy and uncommon neonatal metabolic disorder (Leigh syndrome). We also summarized the current knowledge on the genetic mechanisms and the manifestation of seizure disorders of SOD and MoCD. In conclusion, if clinical, neuroimaging, and neuropathological findings suggest a possible SOD or related disorder; extensive molecular diagnostics should be performed to confirm the diagnosis. [ABSTRACT FROM AUTHOR]

Alcaligenes faecalis, is an opportunistic, pathogenic, Gram-negative, food-borne bacterium appearing to be of public health importance due to its resistance to common antibiotics and frequent involvement in nosocomial infections and water contamination. Yet, the Betaproteobacterium showed potential benefit in fat degradation of food waste. It is suggested that pterin-based Molybdenum cofactor (Moco) biosynthesis involving moa gene is related with the pathogenesis of several Gram-negative bacteria, while in addition to lipase genes, glycerol coding genes including glpD are involved in effective degradation of fat waste. In this study, a degenerate colony and an arbitrary PCR-based methods were involved in gene isolation steps. We designed a pair of degenerate primers to detect moaC (GMF: 5′-ATCGGCATCACCAACCAGC-3′ and GMR: 5′-TGTCGATGGTGCCGAAGC-3′) and two gene specific primers to amplify 5′ (5′-TGATGAATGTTCCGTTGCGCTGCC-3′) and 3′ (5′-GACCTGCAGGCATGCAAGCTCGGC-3′) ends of glpD of strain JG3 using degenerate colony and arbitrary PCR methods, respectively. The developed degenerate colony PCR resulted amplification of targeted 421-bp DNA, while the set arbitrary PCR resulted in non-targeted 436-bp DNA. Deduced amino acid analysis showed that both sequences shared 94% amino acid similarity with molybdenum cofactor biosynthesis (MoaC) of Pseudomonas stutzeri and benzoate membrane transporter (BenE) of A. faecalis, respectively. Practical applications It is suggested that pterin-based Molybdenum cofactor (Moco) biosynthesis involving moa gene is related with the pathogenesis of several Gram-negative bacteria, while in addition to lipase genes, glycerol coding genes including glpD are involved in effective degradation of fat waste. However, information about these genes in pathogenic, food-borne, Gram-negative Alcaligenes sp. JG3 bacterium originated from root of Zea mays is barely found. A pair of degenerate primers (GMF: 5′-ATCGGCATCACCAACCAGC-3′ and GMR: 5′-TGTCGATGGTGCCGAAGC-3′) designed in this study could detect 421-bp moaC gene fragment using degenerate colony PCR, while another pair of gene specific primers 5′ (5′-TGATGAATGTTCCGTTGCGCTGCC-3′) and 3′ (5′-GACCTGCAGGCATGCAAGCTCGGC-3′) aiming to amplify ends of glpD of Alcaligenes sp. JG3 detected a nontargeted, 436-bp benE gene of the strain using an arbitrary PCR method. [ABSTRACT FROM AUTHOR]

The biosynthesis of the molybdenum cofactor (Moco) is a highly conserved pathway in bacteria, archaea and eukaryotes. The molybdenum atom in Moco-containing enzymes is coordinated to the dithiolene group of a tricyclic pyranopterin monophosphate cofactor. The biosynthesis of Moco can be divided into three conserved steps, with a fourth present only in bacteria and archaea: (1) formation of cyclic pyranopterin monophosphate, (2) formation of molybdopterin (MPT), (3) insertion of molybdenum into MPT to form Mo-MPT, and (4) additional modification of Mo-MPT in bacteria with the attachment of a GMP or CMP nucleotide, forming the dinucleotide variants of Moco. While the proteins involved in the catalytic reaction of each step of Moco biosynthesis are highly conserved among the Phyla, a surprising link to other cellular pathways has been identified by recent discoveries. In particular, the pathways for FeS cluster assembly and thio-modifications of tRNA are connected to Moco biosynthesis by sharing the same protein components. Further, proteins involved in Moco biosynthesis are not only shared with other pathways, but additionally have moonlighting roles. This review gives an overview of Moco biosynthesis in bacteria and humans and highlights the shared function and moonlighting roles of the participating proteins. [ABSTRACT FROM AUTHOR]

Viperin is an IFN-inducible radical S-adenosylmethionine (SAM) enzyme that inhibits viral replication. We determined crystal structures of an anaerobically prepared fragment of mouse viperin (residues 45-362) complexed with S-adenosylhomocysteine (SAH) or 5'-deoxyadenosine (5'-dAdo) and L-methionine (L-Met). Viperin contains a partial (βα)6-barrel fold with a disordered N-terminal extension (residues 45-74) and a partially ordered C-terminal extension (residues 285-362) that bridges the partial barrel to form an overall closed barrel structure. Cys84, Cys88, and Cys91 located after the first β-strand bind a [4Fe-4S] cluster. The active site architecture of viperin with bound SAH (a SAM analog) or 5'-dAdo and L-Met (SAM cleavage products) is consistent with the canonical mechanism of 5'-deoxyadenosyl radical generation. The viperin structure, together with sequence alignments, suggests that vertebrate viperins are highly conserved and that fungi contain a viperin-like ortholog. Many bacteria and archaebacteria also express viperin-like enzymes with conserved active site residues. Structural alignments show that viperin is similar to several other radical SAM enzymes, including the molybdenum cofactor biosynthetic enzyme MoaA and the RNA methyltransferase RlmN, which methylates specific nucleotides in rRNA and tRNA. The viperin putative active site contains several conserved positively charged residues, and a portion of the active site shows structural similarity to the GTPbinding site of MoaA, suggesting that the viperin substrate may be a nucleoside triphosphate of some type. [ABSTRACT FROM AUTHOR]

Modifications of transfer RNA (tRNA) have been shown to play critical roles in the biogenesis, metabolism, structural stability and function of RNA molecules, and the specific modifications of nucleobases with sulfur atoms in tRNA are present in pro- and eukaryotes. Here, especially the thiomodifications xm5s2U at the wobble position 34 in tRNAs for Lys, Gln and Glu, were suggested to have an important role during the translation process by ensuring accurate deciphering of the genetic code and by stabilization of the tRNA structure. The trafficking and delivery of sulfur nucleosides is a complex process carried out by sulfur relay systems involving numerous proteins, which not only deliver sulfur to the specific tRNAs but also to other sulfur-containing molecules including iron-sulfur clusters, thiamin, biotin, lipoic acid and molybdopterin (MPT). Among the biosynthesis of these sulfur-containing molecules, the biosynthesis of the molybdenum cofactor (Moco) and the synthesis of thio-modified tRNAs in particular show a surprising link by sharing protein components for sulfur mobilization in pro- and eukaryotes. [ABSTRACT FROM AUTHOR]

The sulfur-containing amino acid homocysteine is a cardiac risk factor and a biomarker for several inborn errors of metabolism in methionine synthesis. A simple LC-MS/MS method was developed and validated for determination of homocysteine and methionine in human plasma. Rapid separation was achieved using a reverse phase liquid chromatography. Mass spectrometry identification was performed in positive electrospray ionization mode for homocysteine and methionine. Accuracy, precision, linearity, recovery and sample stability were evaluated in the method validation. The test is applied in diagnosis of homocystinuria and monitoring total homocysteine levels. Moreover, simultaneous measurement of methionine helps in the differentiation of homocystinuria and some cobalamin disorders (such as cblC and cblD defects) without additional amino acid testing. Lastly, this assay is sensitive to detect reduced total homocysteine levels that are possibly seen in sulfocysteinuria and molybdenum cofactor deficiencies. [ABSTRACT FROM AUTHOR]