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The retention mechanisms of nitrobenzofurazan (NBD)-amino acids in reversed-phase ion-pair liquid chromatography were quantitatively analyzed in silico. The most contributed interaction for the retention is the Lewis acid-base interaction between an aromatic ring of NBD-amino acids and hydroxyl-group hydrogen of tetra-butyl-ammonium hydroxide coated on the hydrophobic phase. Solvent effects significantly improved the relation between the calculated molecular interaction (MI) energy values using a molecular mechanics program and log k values measured in chromatography. The correlation coefficient between the calculated MI energy values and the log k values was >0.95. [ABSTRACT FROM AUTHOR]

Background: Alterations in one-carbon metabolism (OCM) have been observed in patients with schizophrenia (SZ), but a comprehensive study of OCM has not yet been conducted. A carbon atom is transferred from l-serine to methionine during OCM, but the relationship between l-serine and methionine in SZ is not yet known. We investigated the relationship between l-serine and methionine to obtain a comprehensive understanding of OCM in SZ. Methods: We recruited forty-ive patients with SZ and thirty normal controls (NC). Whole blood, plasma, and DNA specimens were obtained from all participants. Plasma l-serine, d-serine, glycine, methionine, and total homocysteine levels were measured using high-performance liquid chromatography. Plasma vitamin B12 and total folate were measured using a chemiluminescent protein-binding immunoassay. Clinical symptoms were estimated using the positive and negative syndrome scale (PANSS). The methylenetetrahydrofolate reductase (MTHFR) C667T genotype and A298C genotype, which are involved in MTHFR activity, were determined using the TaqMan genotyping assay system. Results: Analysis of variance was used to conirm that the SZ cohort has higher plasma homocysteine levels and lower plasma folate levels than the NC group. Multi-regression analysis revealed a relationship between l-serine and methionine in the NC group but not in the SZ group. The MTHFR genotype did not afect the relationship between l-serine and methionine in each group. The total PANSS score was signiicantly related to d-serine and folate levels and to age. Positive PANSS scores were signiicantly related to both glycine and sex. In addition, both glycine and d-serine were signiicantly correlated with negative PANSS scores. Conclusions: We found impairment of the relationship between l-serine and methionine in SZ. Clinical symptoms of SZ were partially correlated with the OCM components. These indings contributed to our understanding of OCM alteration in SZ and may explain why the alteration occurs. [ABSTRACT FROM AUTHOR]

Various D-amino acids play important physiological roles in mammals, but the pathways of their production remain unknown except for d-serine, which is generated by serine racemase. Previously, we found that Escherichia coli cystathionine β-lyase possesses amino acid racemase activity in addition to β-lyase activity. In the present work, we evaluated the enzymatic activities of human cystathionine γ-lyase, which shares a relatively high amino acid sequence identity with cystathionine β-lyase. The enzyme did not show racemase activity toward various amino acids including alanine and lyase and dehydratase activities were highest toward L-cystathionine and L-homoserine, respectively. The enzyme also showed weak activity toward L-cysteine and L-serine but no activity toward D-amino acids. Intriguingly, the pH and temperature profiles of lyase activity were distinct from those of dehydratase activity. Catalytic efficiency was higher for lyase activity than for dehydratase activity. [ABSTRACT FROM AUTHOR]

Recent investigations have shown that multiple D-amino acids are present in mammals and these compounds have distinctive physiological functions. Free D-glutamate is present in various mammalian tissues and cells and in particular, it is presumably correlated with cardiac function, and much interest is growing in its unique metabolic pathways. Recently, we first identified D-glutamate cyclase as its degradative enzyme in mammals, whereas its biosynthetic pathway in mammals is unclear. Glutamate racemase is a most probable candidate, which catalyzes interconversion between D-glutamate and L-glutamate. Here, we identified the cDNA encoding L-serine dehydratase-like (SDHL) as the first mammalian clone with glutamate racemase activity. This rat SDHL had been deposited in mammalian databases as a protein of unknown function and its amino acid sequence shares ~60% identity with that of L-serine dehydratase. Rat SDHL was expressed in Escherichia coli, and the enzymatic properties of the recombinant were characterized. The results indicated that rat SDHL is a multifunctional enzyme with glutamate racemase activity in addition to L-serine/L-threonine dehydratase activity. This clone is hence abbreviated as STDHgr. Further experiments using cultured mammalian cells confirmed that D-glutamate was synthesized and L-serine and L-threonine were decomposed. It was also found that SDHL (STDHgr) contributes to the homeostasis of several other amino acids. [ABSTRACT FROM AUTHOR]

D-Serine (D-Ser) is a coagonist for NMDA-type glutamate receptors and is thus important for higher brain function. D-Ser is synthesized by serine racemase and degraded by D-amino acid oxidase. However, the significance of these enzymes and the relevant functions of D-amino acids remain unclear. Here, we show that in the nematode Caenorhabditis elegans, the serine racemase homolog SERR-1 and D-amino acid oxidase DAAO-1 control an adaptive foraging behavior. Similar to many organisms, C. elegans immediately initiates local search for food when transferred to a new environment. With prolonged food deprivation, the worms exhibit a long-range dispersal behavior as the adaptive foraging strategy. We found that serr-1 deletion mutants did not display this behavior, whereas daao-1 deletion mutants immediately engaged in long-range dispersal after food removal. A quantitative analysis of D-amino acids indicated that D-Ser and D-alanine (D-Ala) are both synthesized and suppressed during food deprivation. A behavioral pharmacological analysis showed that the long-range dispersal behavior requires NMDA receptor desensitization. Long-term pretreatment with D-Ala, as well as with an NMDA receptor agonist, expanded the area searched by wild-type worms immediately after food removal, whereas pretreatment with D-Ser did not. We propose that D-Ser and D-Ala are endogenous regulators that cooperatively induce the long-range dispersal behavior in C. elegans through actions on the NMDA receptor. [ABSTRACT FROM AUTHOR]

Non-canonical D-amino acids play important roles in bacteria including control of peptidoglycan metabolism and biofilm disassembly. Bacteria appear to produce non-canonical D-amino acids to adapt to various environmental changes and understanding the biosynthetic pathways is important. We identified novel amino acid racemases possessing the ability to produce non-canonical D-amino acids in Escherichia coli and Bacillus subtilis in our previous study, whereas the biosynthetic pathways of these D-amino acids still remain unclear. In the present study, we demonstrated that two cystathionine β-lyases (MetC and MalY) from E. coli produce non-canonical D-amino acids including non-proteinogenic amino acids. Furthermore, MetC displayed D- and L-serine (Ser) dehydratase activity. We characterised amino acid racemase, Ser dehydratase and cysteine lyase activities and all were higher for MetC. Interestingly, all three activities were at a comparable level for MetC, although optimal conditions for each reaction were distinct. These results indicate that MetC and MalY are multifunctional enzymes involved in L-methionine metabolism and the production of D-amino acids, as well as D- and L-Ser metabolism. To our knowledge, this is the first evidence that cystathionine β-lyase is a multifunctional enzyme with three different activities. [ABSTRACT FROM AUTHOR]

d-Aspartate oxidase (DDO) is a degradative enzyme thatis stereospecific for acidic d-amino acids, including d-aspartate, a potential agonist of the N-methyl-d-aspartate (NMDA) receptor. Dysfunction of NMDA receptor-mediatedneurotransmission has been implicated in the onset of various mentaldisorders, such as schizophrenia. Hence, a DDO inhibitor that increasesthe brain levels of d-aspartate and thereby activates NMDAreceptor function is expected to be a useful compound. To search forpotent DDO inhibitor(s), a large number of compounds were screened in silico, and several compounds were identified as candidates.They were then characterized and evaluated as novel DDO inhibitors in vitro(e.g., the inhibitor constant value of 5-aminonicotinicacid for human DDO was 3.80 μM). The present results indicatethat some of these compounds may serve as lead compounds for the developmentof a clinically useful DDO inhibitor and as active site probes toelucidate the structure–function relationships of DDO. [ABSTRACT FROM AUTHOR]

D-Amino add oxidase (DAO) is a degradative enzyme that is stereospecific for D-amino acids, including D-serine and D-alanine, which are believed to be coagonists of the N-methyl-D-aspartate (NMDA) receptor. To identify a new class of DAO inhibitor(s) that can be used to eluddate the molecular details of the active site environment of DAO, manifold biologically active compounds of microbial origin and pre-existing drugs were screened for their ability to inhibit DAO activity, and several compounds were identified as candidates. One of these compounds, acydowr (ACV), a well-known antiviral drug used for the treatment of herpesvirus infections, was characterized and evaluated as a novel DAO inlubitor in vitro. Analysis showed that ACV acts on DAO as a reversible slow-binding inhibitor, and interesting, the time required to achieve equilibrium between DAO, ACV, and the DAO/ACV complex was highly dependent on temperature. The binding mechanism of ACV to DAO was investigated in detail by several approaches, including kinetic analysis, structural modeling of DAO complexed with ACV, and site-specific mutagenesis of an active site residue postulated to be involved in the binding of ACV. The results confirm that ACV is a novel, active site-directed inhibitor of DAO that can be a valuable tool for investigating the structure-function relationships of DAO, including the molecular details of the active site environment of DAO. In particular, it appears that ACV can serve as an active site probe to study the structural basis of temperature-induced conformational changes of DAO. [ABSTRACT FROM AUTHOR]