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Keenan BT, Galante RJ, Lian J, Zhang L, Guo X, Veatch OJ, Chesler EJ, O'Brien WT, Svenson KL, Churchill GA, Pack AI. The dihydropyrimidine dehydrogenase gene contributes to heritable differences in sleep in mice. Curr Biol 2021; 31:5238-5248.e7. [PMID: 34653361 DOI: 10.1016/j.cub.2021.09.049] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 08/25/2021] [Accepted: 09/17/2021] [Indexed: 12/27/2022]
Abstract
Many aspects of sleep are heritable, but only a few sleep-regulating genes have been reported. Here, we leverage mouse models to identify and confirm a previously unreported gene affecting sleep duration-dihydropyrimidine dehydrogenase (Dpyd). Using activity patterns to quantify sleep in 325 Diversity Outbred (DO) mice-a population with high genetic and phenotypic heterogeneity-a linkage peak for total sleep in the active lights off period was identified on chromosome 3 (LOD score = 7.14). Mice with the PWK/PhJ ancestral haplotype at this location demonstrated markedly reduced sleep. Among the genes within the linkage region, available RNA sequencing data in an independent sample of DO mice supported a highly significant expression quantitative trait locus for Dpyd, wherein reduced expression was associated with the PWK/PhJ allele. Validation studies were performed using activity monitoring and EEG/EMG recording in Collaborative Cross mouse strains with and without the PWK/PhJ haplotype at this location, as well as EEG and EMG recording of sleep and wake in Dpyd knockout mice and wild-type littermate controls. Mice lacking Dpyd had 78.4 min less sleep during the lights-off period than wild-type mice (p = 0.007; Cohen's d = -0.94). There was no difference in other measured behaviors in knockout mice, including assays evaluating cognitive-, social-, and affective-disorder-related behaviors. Dpyd encodes the rate-limiting enzyme in the metabolic pathway that catabolizes uracil and thymidine to β-alanine, an inhibitory neurotransmitter. Thus, data support β-alanine as a neurotransmitter that promotes sleep in mice.
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Affiliation(s)
- Brendan T Keenan
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Raymond J Galante
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Jie Lian
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Lin Zhang
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Xiaofeng Guo
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Olivia J Veatch
- Department of Psychiatry & Behavioral Sciences, University of Kansas Medical Center, Kansas City, KS, USA
| | | | - W Timothy O'Brien
- Neurobehavior Testing Core, Institute for Translational and Therapeutic Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | | | | | - Allan I Pack
- Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
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2
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Seino Y, Ohashi N, Kohno T. The endogenous agonist, β-alanine, activates glycine receptors in rat spinal dorsal neurons. Biochem Biophys Res Commun 2018; 500:897-901. [DOI: 10.1016/j.bbrc.2018.04.183] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 04/23/2018] [Indexed: 11/26/2022]
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3
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Hano T, Ito K, Kono K, Ito M, Ohkubo N, Mochida K. Effect of taurine supplementation on hepatic metabolism and alleviation of cadmium toxicity and bioaccumulation in a marine teleost, red sea bream, Pagrus major. FISH PHYSIOLOGY AND BIOCHEMISTRY 2017; 43:137-152. [PMID: 27535560 DOI: 10.1007/s10695-016-0274-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Accepted: 08/08/2016] [Indexed: 06/06/2023]
Abstract
This study was performed to unravel the mechanism of the beneficial action of taurine on marine teleost fish, red sea bream (Pagrus major), by analyzing the hepatic metabolism. Moreover, the ameliorative effects of the nutrient against cadmium toxicity and bioaccumulation were further evaluated. The fish were fed a diet containing 0 % (TAU0 %), 0.5 % (TAU0.5 %), or 5.0 % (TAU5.0 %) taurine for 40-55 days (d) and subjected to cadmium acute toxicity and bioaccumulation tests. Taurine deficiency in feed severely affected growth and the hepatic metabolic profiles of the fish, including a remarkable increase in myo-inositol, aspartate, and ß-alanine in the TAU0 % group, which indicates a complementary physiological response to taurine deficiency. For the acute toxicity test, fish were fed the test diets for 55 d and were then exposed to different dose of cadmium ranging from 0 to 5.6 mg/L for 96 h. Fish fed taurine had a higher tolerance to cadmium than those not fed taurine. For the bioaccumulation test, fish were fed the test diets for 40 d and then were chronically exposed to 0.2 mg/L of cadmium for 28 d followed by depuration for 21 d. Cadmium concentrations in the liver and muscle of fish fed TAU5.0 % were significantly lower than those of fish fed TAU0 % for the first 7 d of exposure and the first 7 d of elimination. Our findings suggest a possible mechanism for the beneficial role played by taurine and that the inclusion of taurine in fish aquaculture feed may reduce cadmium contamination of fish intended for human consumption.
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Affiliation(s)
- Takeshi Hano
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan.
| | - Katsutoshi Ito
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
| | - Kumiko Kono
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
| | - Mana Ito
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
| | - Nobuyuki Ohkubo
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
| | - Kazuhiko Mochida
- National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research and Education Agency, 2-17-5, Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
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4
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Juge N, Omote H, Moriyama Y. Vesicular GABA transporter (VGAT) transports β-alanine. J Neurochem 2013; 127:482-6. [PMID: 23919636 DOI: 10.1111/jnc.12393] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/01/2013] [Accepted: 08/01/2013] [Indexed: 11/28/2022]
Abstract
Vesicular GABA transporter (VGAT) is expressed in GABAergic and glycinergic neurons, and is responsible for vesicular storage and subsequent exocytosis of these inhibitory amino acids. In this study, we show that VGAT recognizes β-alanine as a substrate. Proteoliposomes containing purified VGAT transport β-alanine using Δψ but not ΔpH as a driving force. The Δψ-driven β-alanine uptake requires Cl(-). VGAT also facilitates Cl(-) uptake in the presence of β-alanine. A previously described VGAT mutant (Glu213Ala) that disrupts GABA and glycine transport similarly abrogates β-alanine uptake. These findings indicated that VGAT transports β-alanine through a mechanism similar to those for GABA and glycine, and functions as a vesicular β-alanine transporter. Vesicular GABA transporter (VGAT) is expressed in GABAergic and glycinergic neurons, and is responsible for vesicular storage and subsequent exocytosis of these inhibitory amino acids. In the present study, we showed that proteoliposomes containing purified VGAT transport β-alanine using Δψ as a driving force. VGAT also facilitates Cl(-) uptake. Our findings indicated that VGAT functions as a vesicular β-alanine transporter.
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Affiliation(s)
- Narinobu Juge
- Advanced Research Center, Okayama University, Okayama, Japan
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5
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Shanthi D, Selvarajan P, HemaDurga KK, Lincy Mary Ponmani S. Nucleation kinetics, growth and studies of β-alanine single crystals. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 110:1-6. [PMID: 23548638 DOI: 10.1016/j.saa.2013.02.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/17/2013] [Accepted: 02/15/2013] [Indexed: 06/02/2023]
Abstract
Solubility and metastable zone width for the re-crystallized salt of β-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 °C) was carried out for supersaturated aqueous solutions of β-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of β-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies.
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Affiliation(s)
- D Shanthi
- Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628 216, Tamil Nadu, India
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6
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Zinellu A, Sotgia S, Deiana L, Carru C. Analysis of neurotransmitter amino acids by CE-LIF detection in biological fluids. Methods Mol Biol 2013; 919:35-42. [PMID: 22976088 DOI: 10.1007/978-1-62703-029-8_4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neurotransmitter amino acids like Alanine (Ala), Glutamic acid (Glu), Aspartic acid (Asp), Serine (Ser), Taurine (Tau), and Glycine (Gly) are widely distributed in biological fluids and tissues and they have important physiological functions, so that the evaluation of their levels in organisms plays an essential role in physiology. We here report a new capillary electrophoresis (CE) method with laser-induced fluorescence detection by which analytes are resolved and detected in less than 12 min both in human plasma and in other samples types, such as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva, and vitreous humor, thus avoiding the typical limitations of the other methods normally suitable only in one or two matrix types.
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Affiliation(s)
- Angelo Zinellu
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
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7
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Identification of physiologically active substances as novel ligands for MRGPRD. J Biomed Biotechnol 2012; 2012:816159. [PMID: 23091359 PMCID: PMC3471037 DOI: 10.1155/2012/816159] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/06/2012] [Accepted: 05/05/2012] [Indexed: 12/02/2022] Open
Abstract
Mas-related G-protein coupled receptor member D (MRGPRD) is a G protein-coupled receptor (GPCR) which belongs to the Mas-related GPCRs expressed in the dorsal root ganglia (DRG). In this study, we investigated two novel ligands in addition to beta-alanine: (1) beta-aminoisobutyric acid, a physiologically active substance, with which possible relation to tumors has been seen together with beta-alanine; (2) diethylstilbestrol, a synthetic estrogen hormone. In addition to the novel ligands, we found that transfection of MRGPRD leads fibroblast cells to form spheroids, which would be related to oncogenicity. To understand the MRGPRD novel character, oncogenicity, a large chemical library was screened in order to obtain MRGPRD antagonists to utilize in exploring the character. The antagonist in turn inhibited the spheroid proliferation that is dependent on MRGPRD signaling as well as MRGPRD signals activated by beta-alanine. The antagonist, a small-molecule compound we found in this study, is a potential anticancer agent.
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8
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Stepanian SG, Ivanov AY, Smyrnova DA, Adamowicz L. UV-induced isomerization of β-alanine isolated in argon matrices. J Mol Struct 2012. [DOI: 10.1016/j.molstruc.2012.04.093] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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9
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Stone TW, Lui C, Addae JI. Effects of ethylenediamine--a putative GABA-releasing agent--on rat hippocampal slices and neocortical activity in vivo. Eur J Pharmacol 2011; 650:568-78. [PMID: 21050846 DOI: 10.1016/j.ejphar.2010.10.061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 10/26/2010] [Accepted: 10/27/2010] [Indexed: 10/18/2022]
Abstract
The simple diamine diaminoethane (ethylenediamine, EDA) has been shown to activate GABA receptors in the central and peripheral nervous systems, partly by a direct action and partly by releasing endogenous GABA. These effects have been shown to be produced by the complexation of EDA with bicarbonate to form a carbamate. The present work has compared EDA, GABA and β-alanine responses in rat CA1 neurons using extracellular and intracellular recordings, as well as neocortical evoked potentials in vivo. Superfusion of GABA onto hippocampal slices produced depolarisation and a decrease of field epsps, both effects fading rapidly, but showing sensitivity to blockade by bicuculline. EDA produced an initial hyperpolarisation and increase of extracellular field epsp size with no fade and only partial sensitivity to bicuculline, with subsequent depolarisation, while β-alanine produces a much larger underlying hyperpolarisation and increase in fepsps, followed by depolarisation and inhibition of fepsps. The responses to β-alanine, but not GABA or EDA, were blocked by strychnine. In vivo experiments, recording somatosensory evoked potentials, confirmed that EDA produced an initial increase followed by depression, and that this effect was not fully blocked by bicuculline. Overall the results indicate that EDA has actions in addition to the activation of GABA receptors. These actions are not attributable to activation of β-alanine-sensitive glycine receptors, but may involve the activation of sites sensitive to adipic acid, which is structurally equivalent to the dicarbamate of EDA. The results emphasise the complex pharmacology of simple amines in bicarbonate-containing solutions.
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Affiliation(s)
- Trevor W Stone
- Neuroscience and Molecular Pharmacology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
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10
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Zinellu A, Sotgia S, Pisanu E, Scanu B, Sanna M, Usai MF, Chessa R, Deiana L, Carru C. Quantification of neurotransmitter amino acids by capillary electrophoresis laser-induced fluorescence detection in biological fluids. Anal Bioanal Chem 2010; 398:1973-8. [PMID: 20803002 DOI: 10.1007/s00216-010-4134-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 08/13/2010] [Accepted: 08/15/2010] [Indexed: 10/19/2022]
Abstract
The role of neurotransmitter amino acids (NAAs) in the functioning of the nervous system has been the focus of increasingly intense research over the past several years. Among the various amino acids that have important roles as neurotransmitters, there are alanine (Ala), glutamic acid (Glu), aspartic acid (Asp), serine (Ser), taurine (Tau) and glycine (Gly). NAAs are present in plasma, cells and--at trace levels--in all biological fluids, but complex components in biological matrices make it difficult to determine them in biological samples. We describe a new capillary electrophoresis (CE) method with laser-induced fluorescence detection by which analytes are resolved in less than 12 minutes in a 18 mmol/L phosphate run buffer at pH 11.6. The use of elevated temperatures during sample derivatization leads to a drastic reduction in the reaction time, down to 20 min, compared to the 6-14 h usually described for reactions between FITC and amino acids at room temperature. In order to demonstrate its wide range of applications, the method was applied to the analysis of NAA in human plasma and in other sample types, such as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva and vitreous humor, thus avoiding the typical limitations of other methods, which are normally suitable for use with only one or two matrix types.
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Affiliation(s)
- Angelo Zinellu
- Department Biomedical Sciences and Centre of Excellence for Biotechnology Development and Biodiversity Research, University of Sassari, Viale San Pietro 43/B, 07100 Sassari, Italy
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11
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Beck H, Dobritzsch D, Piškur J. Saccharomyces kluyverias a model organism to study pyrimidine degradation. FEMS Yeast Res 2008; 8:1209-13. [DOI: 10.1111/j.1567-1364.2008.00442.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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12
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Lundgren S, Lohkamp B, Andersen B, Piskur J, Dobritzsch D. The crystal structure of beta-alanine synthase from Drosophila melanogaster reveals a homooctameric helical turn-like assembly. J Mol Biol 2008; 377:1544-59. [PMID: 18336837 DOI: 10.1016/j.jmb.2008.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 02/06/2008] [Accepted: 02/07/2008] [Indexed: 11/29/2022]
Abstract
Beta-alanine synthase (betaAS) is the third enzyme in the reductive pyrimidine catabolic pathway, which is responsible for the breakdown of the nucleotide bases uracil and thymine in higher organisms. It catalyzes the hydrolysis of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyrate to the corresponding beta-amino acids. betaASs are grouped into two phylogenetically unrelated subfamilies, a general eukaryote one and a fungal one. To reveal the molecular architecture and understand the catalytic mechanism of the general eukaryote betaAS subfamily, we determined the crystal structure of Drosophila melanogaster betaAS to 2.8 A resolution. It shows a homooctameric assembly of the enzyme in the shape of a left-handed helical turn, in which tightly packed dimeric units are related by 2-fold symmetry. Such an assembly would allow formation of higher oligomers by attachment of additional dimers on both ends. The subunit has a nitrilase-like fold and consists of a central beta-sandwich with a layer of alpha-helices packed against both sides. However, the core fold of the nitrilase superfamily enzymes is extended in D. melanogaster betaAS by addition of several secondary structure elements at the N-terminus. The active site can be accessed from the solvent by a narrow channel and contains the triad of catalytic residues (Cys, Glu, and Lys) conserved in nitrilase-like enzymes.
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Affiliation(s)
- Stina Lundgren
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden
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13
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Schnackerz KD, Dobritzsch D. Amidohydrolases of the reductive pyrimidine catabolic pathway purification, characterization, structure, reaction mechanisms and enzyme deficiency. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:431-44. [PMID: 18261476 DOI: 10.1016/j.bbapap.2008.01.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 01/07/2008] [Accepted: 01/09/2008] [Indexed: 12/26/2022]
Abstract
In the reductive pyrimidine catabolic pathway uracil and thymine are converted to beta-alanine and beta-aminoisobutyrate. The amidohydrolases of this pathway are responsible for both the ring opening of dihydrouracil and dihydrothymine (dihydropyrimidine amidohydrolase) and the hydrolysis of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyrate (beta-alanine synthase). The review summarizes what is known about the properties, kinetic parameters, three-dimensional structures and reaction mechanisms of these proteins. The two amidohydrolases of the reductive pyrimidine catabolic pathway have unrelated folds, with dihydropyrimidine amidohydrolase belonging to the amidohydrolase superfamily while the beta-alanine synthase from higher eukaryotes belongs to the nitrilase superfamily. beta-Alanine synthase from Saccharomyces kluyveri is an exception to the rule and belongs to the Acyl/M20 family.
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14
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Alvarez CM, García-Rodríguez R, Miguel D. Carbonyl complexes of manganese, rhenium and molybdenum with 2-pyridylimino acid ligands. J Organomet Chem 2007. [DOI: 10.1016/j.jorganchem.2007.09.025] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Lundgren S, Andersen B, Piskur J, Dobritzsch D. Crystal structures of yeast beta-alanine synthase complexes reveal the mode of substrate binding and large scale domain closure movements. J Biol Chem 2007; 282:36037-47. [PMID: 17916556 DOI: 10.1074/jbc.m705517200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Beta-alanine synthase is the final enzyme of the reductive pyrimidine catabolic pathway, which is responsible for the breakdown of uracil and thymine in higher organisms. The fold of the homodimeric enzyme from the yeast Saccharomyces kluyveri identifies it as a member of the AcyI/M20 family of metallopeptidases. Its subunit consists of a catalytic domain harboring a di-zinc center and a smaller dimerization domain. The present site-directed mutagenesis studies identify Glu(159) and Arg(322) as crucial for catalysis and His(262) and His(397) as functionally important but not essential. We determined the crystal structures of wild-type beta-alanine synthase in complex with the reaction product beta-alanine, and of the mutant E159A with the substrate N-carbamyl-beta-alanine, revealing the closed state of a dimeric AcyI/M20 metallopeptidase-like enzyme. Subunit closure is achieved by a approximately 30 degrees rigid body domain rotation, which completes the active site by integration of substrate binding residues that belong to the dimerization domain of the same or the partner subunit. Substrate binding is achieved via a salt bridge, a number of hydrogen bonds, and coordination to one of the zinc ions of the di-metal center.
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Affiliation(s)
- Stina Lundgren
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden
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16
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Lundgren S, Andersen B, Piškur J, Dobritzsch D. Crystallization and preliminary X-ray data analysis of beta-alanine synthase from Drosophila melanogaster. Acta Crystallogr Sect F Struct Biol Cryst Commun 2007; 63:874-7. [PMID: 17909293 PMCID: PMC2339735 DOI: 10.1107/s1744309107042984] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 09/03/2007] [Indexed: 11/11/2022]
Abstract
Beta-alanine synthase catalyzes the last step in the reductive degradation pathway for uracil and thymine, which represents the main clearance route for the widely used anticancer drug 5-fluorouracil. Crystals of the recombinant enzyme from Drosophila melanogaster, which is closely related to the human enzyme, were obtained by the hanging-drop vapour-diffusion method. They diffracted to 3.3 A at a synchrotron-radiation source, belong to space group C2 (unit-cell parameters a = 278.9, b = 95.0, c = 199.3 A, beta = 125.8 degrees) and contain 8-10 molecules per asymmetric unit.
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Affiliation(s)
- Stina Lundgren
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Birgit Andersen
- Department of Organism and Cell Biology, Lund University, Lund, Sweden
| | - Jure Piškur
- Department of Organism and Cell Biology, Lund University, Lund, Sweden
| | - Doreen Dobritzsch
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
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17
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Lohkamp B, Andersen B, Piškur J, Dobritzsch D. The crystal structures of dihydropyrimidinases reaffirm the close relationship between cyclic amidohydrolases and explain their substrate specificity. J Biol Chem 2006; 281:13762-13776. [PMID: 16517602 DOI: 10.1074/jbc.m513266200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes, dihydropyrimidinase catalyzes the second step of the reductive pyrimidine degradation, the reversible hydrolytic ring opening of dihydropyrimidines. Here we describe the three-dimensional structures of dihydropyrimidinase from two eukaryotes, the yeast Saccharomyces kluyveri and the slime mold Dictyostelium discoideum, determined and refined to 2.4 and 2.05 angstroms, respectively. Both enzymes have a (beta/alpha)8-barrel structural core embedding the catalytic di-zinc center, which is accompanied by a smaller beta-sandwich domain. Despite loop-forming insertions in the sequence of the yeast enzyme, the overall structures and architectures of the active sites of the dihydropyrimidinases are strikingly similar to each other, as well as to those of hydantoinases, dihydroorotases, and other members of the amidohydrolase superfamily of enzymes. However, formation of the physiologically relevant tetramer shows subtle but nonetheless significant differences. The extension of one of the sheets of the beta-sandwich domain across a subunit-subunit interface in yeast dihydropyrimidinase underlines its closer evolutionary relationship to hydantoinases, whereas the slime mold enzyme shows higher similarity to the noncatalytic collapsin-response mediator proteins involved in neuron development. Catalysis is expected to follow a dihydroorotase-like mechanism but in the opposite direction and with a different substrate. Complexes with dihydrouracil and N-carbamyl-beta-alanine obtained for the yeast dihydropyrimidinase reveal the mode of substrate and product binding and allow conclusions about what determines substrate specificity, stereoselectivity, and the reaction direction among cyclic amidohydrolases.
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Affiliation(s)
- Bernhard Lohkamp
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden
| | - Birgit Andersen
- Department of Cell and Organism Biology, Lund University, SE-22362 Lund, Sweden
| | - Jure Piškur
- Department of Cell and Organism Biology, Lund University, SE-22362 Lund, Sweden
| | - Doreen Dobritzsch
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden.
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Sanz ME, Lesarri A, Peña MI, Vaquero V, Cortijo V, López JC, Alonso JL. The Shape of β-Alanine. J Am Chem Soc 2006; 128:3812-7. [PMID: 16536557 DOI: 10.1021/ja058194b] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The combination of Fourier transform microwave spectroscopy in a pulsed supersonic jet with laser ablation has made beta-alanine amenable to a structural study in the gas phase. Two new conformers of beta-alanine have been identified together with the two previously observed by McGlone and Godfrey [J. Am. Chem. Soc. 1995, 117, 1043]. The comparison between the experimental rotational and 14N nuclear quadrupole coupling constants and those calculated ab initio provide a definitive test for molecular structures and confirm unambiguously the identification of all conformers. For the two most abundant conformers, an intramolecular hydrogen bond between the amino group and carbonyl oxygen (N-H...O=C) is established, and the COOH adopts a cis-COOH configuration. The next conformer in order of abundance presents an O-H...N intramolecular hydrogen bond with a trans configuration for the COOH group. The high sensitivity of the experiment has allowed us to detect for the first time a conformer uniquely stabilized by an n-pi* hyperconjugative interaction between the nucleophile N: of the amino group and the pi* orbital at the carbonyl group. Partial conformational relaxation has been observed in the supersonic expansion.
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Affiliation(s)
- M Eugenia Sanz
- Grupo de Espectroscopía Molecular, Departamento de Química Física y Química Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
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19
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Abstract
Ten low-lying conformers of beta-alanine have been studied by the hybrid density functional B3LYP/aug-cc-pVDZ method. Energetic extrapolation calculations at the MP3 and MP4(SDQ) levels of theory and the theoretical photoelectron spectra simulated with the electron propagation theory demonstrate that there are at least three gauche conformers (G1, G2, and G3) in gas-phase experiments. The calculated ionization potentials are in good agreement with the experimental data available in the literature. Natural bond orbital and atoms-in-molecules analyses exhibit a remarkable influence on the molecular electronic structures by the strong intramolecular hydrogen bonding O-H...N in the neutral conformer G2. Remarkable internal rotations of the COOH group are found in the cationic G1+ and G3+ with respect to the neutral conformers. A distonic [NH3+-(CH2)2-COO*] radical can be formed through the spontaneous intramolecular proton transfer in G2+. A novel intramolecular hydrogen bonding, C-H...O, is found in the anti A1+ cation.
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Affiliation(s)
- Shan Xi Tian
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Bond Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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20
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Cruz-Torres A, Galano A, Alvarez-Idaboy JR. Kinetics and mechanism of the β-alanine + OH gas phase reaction: A quantum mechanical approach. Phys Chem Chem Phys 2006; 8:285-92. [PMID: 16482271 DOI: 10.1039/b507101a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The OH hydrogen abstraction reaction from beta-alanine has been studied using the BHandHLYP hybrid HF-density functional and 6-311G(d,p) basis sets. The energies have been improved by single point calculations at the CCSD(T)/6-311G(d,p) level of theory. The structures of the different stationary points are discussed. Reaction profiles are modeled including the formation of pre-reactive and product complexes. Negative net activation energy is obtained for the overall reaction. A complex mechanism is proposed, and the rate coefficients are calculated using transition state theory over the temperature range of 250-400 K. The rate coefficients are proposed for the first time and it was found that in the gas phase the hydrogen abstraction occurs mainly from the CH(2) group next to the amino end. The following expressions, in cm(3) mol(-1) s(-1), are obtained for the overall rate constants, at 250-400 and 290-310 K, respectively: k(250-400)= 2.36 x 10(-12) exp(340/T), and k(290-310)= 1.296 x 10(-12) exp(743/T). The three parameter expression that best describes the studied reaction is k(250-400)= 1.01 x 10(-21)T(3.09) exp(1374/T). The beta-alanine + OH reaction was found to be 1.5 times faster than the alpha-alanine + OH reaction.
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Affiliation(s)
- Armando Cruz-Torres
- Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, 007730 México D. F., México
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21
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Lohkamp B, Andersen B, Piškur J, Dobritzsch D. Purification, crystallization and X-ray diffraction analysis of dihydropyrimidinase from Dictyostelium discoideum. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 62:36-8. [PMID: 16511257 PMCID: PMC2150923 DOI: 10.1107/s174430910503976x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 11/29/2005] [Indexed: 11/10/2022]
Abstract
Dihydropyrimidinase (EC 3.5.2.2) is the second enzyme in the reductive pyrimidine-degradation pathway and catalyses the hydrolysis of 5,6-dihydrouracil and 5,6-dihydrothymine to the corresponding N-carbamylated beta-amino acids. The recombinant enzyme from the slime mould Dictyostelium discoideum was overexpressed, purified and crystallized by the vapour-diffusion method. One crystal diffracted to better than 1.8 A resolution on a synchrotron source and was shown to belong to space group I222, with unit-cell parameters a = 84.6, b = 89.6, c = 134.9 A and one molecule in the asymmetric unit.
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Affiliation(s)
- Bernhard Lohkamp
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | | | - Jure Piškur
- Department of Cell and Organism Biology, Lund, Sweden
| | - Doreen Dobritzsch
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
- Correspondence e-mail:
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22
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Phillips AM, Smart R, Strauss R, Brembs B, Kelly LE. The Drosophila black enigma: the molecular and behavioural characterization of the black1 mutant allele. Gene 2005; 351:131-42. [PMID: 15878647 DOI: 10.1016/j.gene.2005.03.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Revised: 02/21/2005] [Accepted: 03/14/2005] [Indexed: 11/25/2022]
Abstract
The cuticular melanization phenotype of black flies is rescued by beta-alanine, but beta-alanine production, by aspartate decarboxylation, was reported to be normal in assays of black mutants, and although black/Dgad2 is expressed in the lamina, the first optic ganglion, no electroretinogram (ERG) or other visual defect has been demonstrated in black flies. The purpose of this study was to investigate the black gene, and protein, in black(1) mutants of Drosophila melanogaster in order to resolve the apparent paradox of the black phenotype. Using black(1) mutant flies we show that (1) aspartate decarboxylase activity is significantly reduced in adults and at puparium formation, consistent with defects in cuticular and non-cuticular processes, (2) that the black(1) mutation is a frameshift, and black(1) flies are nulls for the black/DGAD2 protein, and (3) that behavioural experiments using Buridan's paradigm, demonstrate that black responds abnormally to visual cues. No ERG, or target recognition defects can be demonstrated suggesting a problem with higher order visual functions in black mutants.
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Affiliation(s)
- A Marie Phillips
- Department of Genetics, University of Melbourne, Parkville, Victoria, Australia.
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23
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Kao CH, Hsu WH. A gene cluster involved in pyrimidine reductive catabolism from Brevibacillus agri NCHU1002. Biochem Biophys Res Commun 2003; 303:848-54. [PMID: 12670488 DOI: 10.1016/s0006-291x(03)00439-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Genes involved in pyrimidine reductive catabolism (pyd) were isolated from a moderate thermophile, Brevibacillus agri NCHU1002, and nine ORFs in an 8.2-kb DNA fragment were identified by DNA sequence analysis. The pyd gene cluster included three closely spaced ORFs, designated pydA, pydB, and pydC, transcribed in the same orientation. Based on their amino acid sequence identity and enzyme activity assay, the gene products were identified as dihydropyrimidine dehydrogenase (PydA), dihydropyrimidinase (PydB), and beta-alanine synthase (PydC). Northern blot and primer extension analyses revealed that the pydBC genes are induced by dihydrouracil and regulated under the control of sigma(54) recognized promoter at transcriptional level as a polycistronic operon. All results indicate that the pydABC genes participate in the pathway of the pyrimidine reductive catabolism. This is the first bacterial pyd gene cluster to be reported.
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Affiliation(s)
- Chao-Hung Kao
- Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan
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24
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Gojkovic Z, Rislund L, Andersen B, Sandrini MPB, Cook PF, Schnackerz KD, Piskur J. Dihydropyrimidine amidohydrolases and dihydroorotases share the same origin and several enzymatic properties. Nucleic Acids Res 2003; 31:1683-92. [PMID: 12626710 PMCID: PMC152861 DOI: 10.1093/nar/gkg258] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Slime mold, plant and insect dihydropyrimidine amidohydrolases (DHPases, EC 3.5.2.2), which catalyze the second step of pyrimidine and several anti-cancer drug degradations, were cloned and shown to functionally replace a defective DHPase enzyme in the yeast Saccharomyces kluyveri. The yeast and slime mold DHPases were over-expressed, shown to contain two zinc ions, characterized for their properties and compared to those of the calf liver enzyme. In general, the kinetic parameters varied widely among the enzymes, the mammalian DHPase having the highest catalytic efficiency. The ring opening was catalyzed most efficiently at pH 8.0 and competitively inhibited by the reaction product, N-carbamyl-beta-alanine. At lower pH values DHPases catalyzed the reverse reaction, the closing of the ring. Apparently, eukaryote DHPases are enzymatically as well as phylogenetically related to the de novo biosynthetic dihydroorotase (DHOase) enzymes. Modeling studies showed that the position of the catalytically critical amino acid residues of bacterial DHOases and eukaryote DHPases overlap. Therefore, only a few modifications might have been necessary during evolution to convert the unspecialized enzyme into anabolic and catabolic ones.
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Affiliation(s)
- Zoran Gojkovic
- Eukaryote Molecular Biology, BioCentrum-DTU, Technical University of Denmark, Building 301, DK-2800 Lyngby, Denmark
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25
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Fiumara A, van Kuilenburg ABP, Caruso U, Nucifora C, Marzullo E, Barone R, Meli C, van Gennip AH. Dihydropyrimidine dehydrogenase deficiency and acute neurological presentation. J Inherit Metab Dis 2003; 26:407-9. [PMID: 12971429 DOI: 10.1023/a:1025123622821] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Dihydropyrimidine dehydrogenase (DPD) deficiency has been linked to 5-fluorouracil toxicity, but patients may present a wide clinical spectrum. We describe a 1-year-old Tunisian girl with a dramatic onset of neurological symptoms suggesting the possible triggering role of environmental factors.
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Affiliation(s)
- A Fiumara
- Center for Inborn Errors of Metabolism, Department of Paediatrics, University of Catania, Catania, Italy.
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26
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Gojković Z, Sandrini MP, Piskur J. Eukaryotic beta-alanine synthases are functionally related but have a high degree of structural diversity. Genetics 2001; 158:999-1011. [PMID: 11454750 PMCID: PMC1461717 DOI: 10.1093/genetics/158.3.999] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
beta-Alanine synthase (EC 3.5.1.6), which catalyzes the final step of pyrimidine catabolism, has only been characterized in mammals. A Saccharomyces kluyveri pyd3 mutant that is unable to grow on N-carbamyl-beta-alanine as the sole nitrogen source and exhibits diminished beta-alanine synthase activity was used to clone analogous genes from different eukaryotes. Putative PYD3 sequences from the yeast S. kluyveri, the slime mold Dictyostelium discoideum, and the fruit fly Drosophila melanogaster complemented the pyd3 defect. When the S. kluyveri PYD3 gene was expressed in S. cerevisiae, which has no pyrimidine catabolic pathway, it enabled growth on N-carbamyl-beta-alanine as the sole nitrogen source. The D. discoideum and D. melanogaster PYD3 gene products are similar to mammalian beta-alanine synthases. In contrast, the S. kluyveri protein is quite different from these and more similar to bacterial N-carbamyl amidohydrolases. All three beta-alanine synthases are to some degree related to various aspartate transcarbamylases, which catalyze the second step of the de novo pyrimidine biosynthetic pathway. PYD3 expression in yeast seems to be inducible by dihydrouracil and N-carbamyl-beta-alanine, but not by uracil. This work establishes S. kluyveri as a model organism for studying pyrimidine degradation and beta-alanine production in eukaryotes.
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Affiliation(s)
- Z Gojković
- Section of Molecular Microbiology, BioCentrum DTU, DK-2800 Lyngby, Denmark
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27
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Mellor JR, Randall AD. Synaptically Released Neurotransmitter Fails to Desensitize Postsynaptic GABAA Receptors in Cerebellar Cultures. J Neurophysiol 2001; 85:1847-57. [PMID: 11353001 DOI: 10.1152/jn.2001.85.5.1847] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABA concentration jump experiments performed on membrane patches predict that postsynaptic GABAAreceptors will become desensitized following the release of the contents of a single GABA-containing synaptic vesicle. To examine this we used a single synaptic bouton stimulation technique to directly examine whether postsynaptic GABAA receptors in cultured cerebellar granule cells exhibit transmitter-induced desensitization. In a large number of recordings, no evidence was found for desensitization of postsynaptic GABAAreceptors by vesicularly released transmitter. This was the case even when as many as 40 vesicles were released from a single bouton within 1.5 s. In addition, postsynaptic depolarization and application of the benzodiazepine flunitrazepam, manipulations previously shown to enhance desensitization of GABAA receptors, failed to unmask transmitter-induced desensitization. In contrast, a single 2- to 3-s application of a high concentration of exogenous GABA was able to depress synaptic responsiveness for up to 70 s. Furthermore, pharmacological depletion of GABA eliminated inhibitory synaptic communication, suggesting that GABA is the transmitter and the desensitization-resistant inhibitory postsynaptic currents are not mediated by a “nondesensitizing” ligand such as β-alanine. Overall our data indicate that a specific desensitization-resistant population of GABAA receptors are present at postsynaptic sites on cultured cerebellar granule cells.
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Affiliation(s)
- J R Mellor
- Neurobiology Division, Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
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28
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Affiliation(s)
- T W Traut
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599-7260, USA
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29
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Gallardo WG, Hagiwara A, Hara K, Soyano K, Snell TW. GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis. Comp Biochem Physiol A Mol Integr Physiol 2000; 127:301-7. [PMID: 11118940 DOI: 10.1016/s1095-6433(00)00266-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
gamma-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.
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Affiliation(s)
- W G Gallardo
- Graduate School of Marine Science and Engineering, Nagasaki University, Bunkyo 1-14, 852-8131, Nagasaki, Japan.
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30
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Gojkovic Z, Jahnke K, Schnackerz KD, Piskur J. PYD2 encodes 5,6-dihydropyrimidine amidohydrolase, which participates in a novel fungal catabolic pathway. J Mol Biol 2000; 295:1073-87. [PMID: 10656811 DOI: 10.1006/jmbi.1999.3393] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Most fungi cannot use pyrimidines or their degradation products as the sole nitrogen source. Previously, we screened several yeasts for their ability to catabolise pyrimidines. One of them, Saccharomyces kluyveri, was able to degrade the majority of pyrimidines. Here, a series of molecular techniques have been modified to clone pyrimidine catabolic genes, study their expression and purify the corresponding enzymes from this yeast. The pyd2-1 mutant, which lacked the 5,6-dihydropyrimidine amidohydrolase (DHPase) activity, was transformed with wild-type S. kluyveri genomic library. The complementing plasmid contained the full sequence of the PYD2 gene, which exhibited a high level of homology with mammalian DHPases and bacterial hydantoinases. The organisation of PYD2 showed a couple of specific features. The 542-codons open reading frame was interrupted by a 63 bp intron, which does not contain the Saccharomyces cerevisiae branch-point sequence, and the transcripts contained a long 5' untranslated leader with five or six AUG codons. The derived amino acid sequence showed similarities with dihydroorotases, allantoinases and uricases from various organisms. Surprisingly, the URA4 gene from S. cerevisiae, which encodes dihydroorotase, shows greater similarity to PYD2 and other catabolic enzymes than to dihydroorotases from several other non-fungal organisms. The S. kluyveri DHPase was purified to homogeneity and sequencing of the N-terminal region revealed that the purified enzyme corresponds to the PYD2 gene product. The enzyme is a tetramer, likely consisting of similar if not identical subunits each with a molecular mass of 59 kDa. The S. kluyveri DHPase was capable of catalysing both dihydrouracil and dihydrothymine degradation, presumably by the same reaction mechanism as that described for mammalian DHPase. On the other hand, the regulation of the yeast PYD2 gene and DHPase seem to be different from that in other organisms. DHPase activity and Northern analysis demonstrated that PYD2 expression is inducible by dihydrouracil, though not by uracil. Apparently, dihydrouracil and DHPase represent an important regulatory checkpoint of the pyrimidine catabolic pathway in S. kluyveri.
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Affiliation(s)
- Z Gojkovic
- Department of Microbiology Building 301, Technical University of Denmark, Lyngby, DK-2800, Denmark
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31
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Conformational analysis of 5-piperidinevaleric acid, 5-(N-methylpiperidine)valerate and their hydrogen halides by MO calculations, X-ray diffraction and FTIR spectroscopy. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00903-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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32
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Qu Y, Arckens L, Vandenbussche E, Geeraerts S, Vandesande F. Simultaneous determination of total and extracellular concentrations of the amino acid neurotransmitters in cat visual cortex by microbore liquid chromatography and electrochemical detection. J Chromatogr A 1998; 798:19-26. [PMID: 9542123 DOI: 10.1016/s0021-9673(97)01170-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To investigate the influence of a partial sensory deprivation on the total and extracellular concentration of the amino acid neurotransmitters in cat visual cortex, two microbore HPLC methods were developed for the simultaneous determination of aspartate, glutamate, glycine, taurine and gamma-aminobutyric acid in cat brain extracts or microdialysis samples. For the determination of the total neurotransmitter concentrations in the visual cortex, the brains were quickly frozen and 200-microns cryostat sections were made. From these sections tissue samples of 2 x 2 mm2 containing the six cortical layers were dissected out of the central and peripheral parts of area 17. After homogenisation and centrifugation, the supernatants were used for quantitative amino acid analysis using an o-phthalaldehyde-tert.-butylthiol pre-column derivatisation HPLC gradient elution method on a microbore column (100 x 1 mm I.D.; C8) and single electrochemical detection. Microdialysis samples from area 17 were obtained every 15 min using 2-mm probes perfused with synthetic cerebrospinal fluid at a flow-rate of 1 microliter/min. After o-phthalaldehyde-tert.-butylthiol derivatisation they were analysed on a microbore column by isocratic elution and dual electrochemical detection. The instrumentation and the different separation parameters were optimised and standard curve, recovery, analytical precision and detection limits for each neurotransmitter were determined.
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Affiliation(s)
- Y Qu
- Laboratory for Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Belgium
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33
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Repérant J, Rio JP, Ward R, Wasowicz M, Miceli D, Medina M, Pierre J. Enrichment of glutamate-like immunoreactivity in the retinotectal terminals of the viper Vipera aspis: an electron microscope quantitative immunogold study. J Chem Neuroanat 1997; 12:267-80. [PMID: 9243346 DOI: 10.1016/s0891-0618(97)00018-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A post-embedding immunogold study was carried out to estimate the immunoreactivity to glutamate in retinal terminals, P axon terminals and dendrites containing synaptic vesicles in the superficial layers of the optic tectum of Vipera. Retinal terminals, identified following either intraocular injection of tritiated proline, horseradish peroxidase (HRP) or short-term survivals after retinal ablation, were observed to be highly glutamate-immunoreactive. A detailed quantitative analysis showed that about 50% of glutamate immunoreactivity was localized over the synaptic vesicles, 35.8% over mitochondria and 14.2% over the axoplasmic matrix. The close association of immunoreactivity with the synaptic vesicles could indicate that Vipera retino-tectal terminals may use glutamate as their neurotransmitter. P axon terminals and dendrites containing synaptic vesicles, strongly gamma-aminobutyric (GABA)-immunoreactive, were shown to be also moderately glutamate-immunoreactive, but two to three times less than retinal terminals. Moreover, in P axon terminals, the glutamate immunoreactivity was denser over mitochondria than over synaptic vesicles, possibly reflecting the 'metabolic' pool of glutamate, which serves as a precursor in the formation of GABA.
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Affiliation(s)
- J Repérant
- INSERM U-106, Laboratoire de Neuromorphologie, Paris, France
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34
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Conformational analysis of N-methylglycine and N,N-dimethylglycine by ab initio calculations. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0166-1280(96)04732-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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35
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Abstract
Glutamate, GABA and glycine, the major neurotransmitters in CNS, are taken up and stored in synaptic vesicles by a Mg(2+)-ATP dependent process. The main driving force for vesicular glutamate uptake is the membrane potential, whereas both the membrane potential and the proton gradient contribute to the uptake of GABA and glycine. Glutamate is taken up by a specific transporter with no affinity for aspartate. Evans blue and related dyes are competitive inhibitors of the uptake of glutamate. GABA, beta-alanine, and glycine are taken up by the same family of transporter molecules. Aspartate, taurine, and proline are not taken up by any synaptic vesicle preparations. It is suggested that vesicular uptake and release are characteristics that identify these amino acids as neurotransmitters. We also discuss that "quanta" in the brain are not necessarily related the content of neurotransmitter in the synaptic vesicles, but rather to postsynaptic events.
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Affiliation(s)
- E M Fykse
- Norwegian Defence Research Establishment, Division for Environmental Toxicology, Kjeller, Norway.
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36
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Traut TW, Jones ME. Uracil metabolism--UMP synthesis from orotic acid or uridine and conversion of uracil to beta-alanine: enzymes and cDNAs. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1996; 53:1-78. [PMID: 8650301 DOI: 10.1016/s0079-6603(08)60142-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- T W Traut
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599, USA
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Wu FS, Gibbs TT, Farb DH. Dual activation of GABAA and glycine receptors by beta-alanine: inverse modulation by progesterone and 5 alpha-pregnan-3 alpha-ol-20-one. Eur J Pharmacol 1993; 246:239-46. [PMID: 8223947 DOI: 10.1016/0922-4106(93)90037-a] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The differential sensitivity of the glycine and GABAA receptors to modulation by progesterone and 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha) was used to determine whether beta-alanine acts through its own receptor, or through the glycine and/or GABAA receptor(s). The response to beta-alanine resembles the glycine response as it is inhibited by strychnine (a competitive glycine antagonist) or progesterone (a negative modulator of the glycine response). Significantly, the response to beta-alanine also resembles the GABA response in that it is inhibited by 2-(carboxy-3'-propyl)-3-amino-6-paramethoxy-phenylpyridazinium+ ++ bromide (SR-95531; a competitive GABA antagonist) and potentiated by 5 alpha 3 alpha (a positive modulator of the GABA response). The efficacy of beta-alanine at the GABAA receptor is comparable to that of GABA. Similarly, the efficacy of beta-alanine at the glycine receptor is comparable to that of glycine. The greater potency of beta-alanine at the glycine receptor indicates that, if beta-alanine is a neurotransmitter, its effects are more likely to be mediated by glycine receptors than by GABAA receptors. However, activation of the GABAA receptor by beta-alanine may become important in the presence of steroid modulators such as progesterone or 5 alpha 3 alpha.
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Affiliation(s)
- F S Wu
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, MA 02118
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Jahnke K, Podschun B, Schnackerz KD, Kautz J, Cook PF. Acid-base catalytic mechanism of dihydropyrimidinase from pH studies. Biochemistry 1993; 32:5160-6. [PMID: 8494893 DOI: 10.1021/bi00070a027] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pH dependence of kinetic parameters and solvent deuterium isotope effects have been used to probe the mechanism of the dihydropyrimidinase from the liver of pig and calf. The V/K for 5,6-dihydrouracil (DHU) (or the alternative substrate glutarimide) measured with either the native zinc or cadmium-substituted enzymes decreases at both low and high pH giving pK values of about 7.5-8 and 9-10. The low pK value observed in V is perturbed significantly to lower pH (approximately 6), and the high pK is not observed. The binding of glutarate monoamide is optimum when the group with a pK of 7.7 is protonated, and this same group must be protonated for the reverse reaction, that is, formation of DHU from N-carbamoyl-beta-alanine. These data are consistent with a general base mechanism and in addition suggest that the enzyme is present initially with a water bound to the active site zinc. The enzymic general base with a pK of 7.5-8 is required to activate water for nucleophilic attack on the C-4 of 5,6-dihydrouracil which is directly coordinated to the active site zinc. The second group with a pK of 9-10 likely reflects Zn-water ionization of the free enzyme. The water bound to the active site Zn is displaced by reactant binding, and thus the pK of 9-10 is not observed in the V profile. Solvent deuterium isotope effects are near unity on the V/K for the natural substrate 5,6-dihydrouracil, but a finite effect of 1.6 is observed on V.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K Jahnke
- Theodor-Boveri-Institut fuer Biowissenschaften (Biozentrum), Universitaet Wuerzburg, Germany
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Vizuete ML, Steffen V, Machado A, Cano J. Effects of neonatal enucleation on catecholamine and serotonin turnover and amino acid levels in lateral geniculate nucleus and visual cortex of the adult rat. Brain Res 1992; 575:231-7. [PMID: 1373983 DOI: 10.1016/0006-8993(92)90084-m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Changes in turnover of dopamine (DA), noradrenaline (NA) and serotonin (5-hydroxytryptamine (5-HT)) and their metabolites, together with amino acid content, have been studied in dorsal lateral geniculate nucleus (LGNd) and visual cortex (VC) of neonatal enucleated rats. Enucleation increases the 5-HT turnover in LGNd and catecholamine turnover in VC. In contrast, enucleation decreases glutamate (and/or aspartate) content in LGNd and gamma-aminobutyric acid (GABA) in VC. These changes suggest an increase of the inhibitory action of the biogenic amines in LGNd after neonatal enucleation. The decrease of GABA in VC may reflect the importance of GABA in intracortical circuitry.
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Affiliation(s)
- M L Vizuete
- Departamento de Bioquimica, Bromatologia y Toxicologia, Universidad de Sevilla, Spain
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40
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Moffett JR, Williamson LC, Neale JH, Palkovits M, Namboodiri MA. Effect of optic nerve transection on N-acetylaspartylglutamate immunoreactivity in the primary and accessory optic projection systems in the rat. Brain Res 1991; 538:86-94. [PMID: 2018935 DOI: 10.1016/0006-8993(91)90380-e] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Evidence has been presented in recent years that support the hypothesis that N-acetylaspartylglutamate (NAAG) may be involved in synaptic transmission in the optic tract of mammals. Using a modified fixation protocol, we have determined the detailed distribution of NAAG immunoreactivity (NAAG-IR) in retinal ganglion cells and optic projections of the rat. Following optic nerve transection, dramatic losses of NAAG-IR were observed in the neuropil of all retinal target zones including the lateral geniculate nucleus, superior colliculus, nucleus of the optic tract, the dorsal and medial terminal nuclei and suprachiasmatic nucleus. Brain regions were microdissected and NAAG levels measured by a radioimmunoassay (RIA) (IC50: NAAG = 2.5 nM, NAA = 100 microM; smallest detectable amount = 1-2 pg/assay). Large decreases (50-60%) in NAAG levels were detected in the lateral geniculate, superior colliculus and suprachiasmatic nucleus. Moderate losses (25-45%) were noted in the pretectal nucleus and the nucleus of the optic tract. Smaller changes (15-20%) were detected in the paraventricular nucleus and the pretectal area. These results are consistent with a synaptic communication role for NAAG in the visual system.
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Affiliation(s)
- J R Moffett
- Department of Biology, Georgetown University, Washington, DC 20057
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41
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42
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Keller HJ, Do KQ, Zollinger M, Winterhalter KH, Cuénod M. Cysteine: depolarization-induced release from rat brain in vitro. J Neurochem 1989; 52:1801-6. [PMID: 2723635 DOI: 10.1111/j.1471-4159.1989.tb07260.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Compounds released on depolarization in a Ca2+-dependent manner from rat brain slices were screened to identify candidates for neuroactive substances. Lyophilized superfusates were analyzed by reversed-phase HPLC after derivatization with 9-fluorenyl N-succinimidyl carbonate. One of the compounds that showed an increase of concentration in superfusates in the presence of iodoacetamide was identified as the cysteine (Cys) derivative, S-carboxamidomethylcysteine, by fast atom bombardment mass spectrometry and other methods. This stable Cys derivative originates from endogenous, extracellular Cys. The finding led to a method for quantification of Cys in superfusates by immediate cooling of the superfusates to 0 degrees C and reaction of Cys with N-ethylmaleimide. Depolarization-induced Ca2+-dependent release of Cys was most prominent in the neocortex, followed by the mesodiencephalon, striatum, and cerebellum. This suggests that Cys is released from a neuronal compartment and might be involved in neurotransmission.
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Affiliation(s)
- H J Keller
- Brain Research Institute, University of Zürich, Switzerland
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43
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Golden GT, Ferraro TN, Fariello RG, Hare TA. Amino acid profiles in Long-Evans rat superior colliculus, visual cortex, and inferior colliculus. Neurochem Res 1989; 14:465-72. [PMID: 2747837 DOI: 10.1007/bf00964862] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An ultrasensitive triple-column ion-exchange/fluorometric method was utilized to measure the levels of over 30 amino acids and related primary amino compounds in Long-Evans rat superior colliculus (SC), visual cortex (VC) and inferior colliculus (IC). Comparison of levels of amino compounds revealed distinctly different profiles for each region. Major constituents were the neurotransmitters and related compounds glutamate, glutamine, GABA, taurine, aspartate and glycine. Glutathione levels were also relatively high in all three regions. SC exhibited a significantly higher level of GABA and beta-alanine compared to both VC and IC. VC had significantly higher levels of glutamate and taurine. VC exhibited the lowest level of glycine and IC the highest. A time-course experiment using SC documented that levels of eleven of thirty-four compounds, including GABA, were subject to significant postmortem alteration in vitro. SC GABA stability experiments indicated that significant in vitro increases of free GABA levels between 1 and 4 min postmortem were associated with equimolar decreases of conjugated GABA levels.
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Affiliation(s)
- G T Golden
- Research and Neurology Veterans Administration, Coatesville, Pennsylvania 19320
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44
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Kautz J, Schnackerz KD. Purification and properties of 5,6-dihydropyrimidine amidohydrolase from calf liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 181:431-5. [PMID: 2714293 DOI: 10.1111/j.1432-1033.1989.tb14743.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
5,6-Dihydropyrimidine amidohydrolase was isolated from an acetone powder of calf liver and purified to homogeneity. Purification made use of heat treatment, ammonium sulfate fractionation and chromatography on Chelating Sepharose and DEAE-Sepharose with 44% recovery of total activity. The native enzyme has a molecular mass of 217 kDa consisting of four subunits with a molecular mass of 54 kDa each. The amidohydrolase is a metalloenzyme containing one zinc atom/subunit. The enzyme can slowly be inactivated by chelating agents. The kinetic parameters for substrates, 5,6-dihydrouracil, 5,6-dihydrothymine and glutarimide were determined. From log Vmax/KM data, a pKa of 7.6 could be calculated suggesting the formation of a zinc-bound hydroxyl ion which carries out the nucleophilic attack on the C-4 of dihydrouracil.
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Affiliation(s)
- J Kautz
- Physiologisch-Chemisches Institut der Universität Würzburg, Federal Republic of Germany
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45
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Orensanz LM, Ambrosio E, Fernández I, Montero MT. A re-examination of the Na+-independent binding of [3H]beta-alanine to rat brain stem-spinal cord. Neurochem Res 1988; 13:1133-8. [PMID: 3148869 DOI: 10.1007/bf00971630] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The Na+-independent binding of [3H]beta-alanine to rat brain stem plus spinal cord was reinvestigated, in order to study in more detail the characteristics of previously described beta-alanine binding processes. Binding was absent when amino acid-free postnuclear supernatants or crude synaptic membranes were used. Experiments performed with several other Na+-free preparations showed a sole binding component, irrespective of the preparation used. Biochemical characterization of this Na+-independent binding, using frozen/thawed/washed synaptosomal-mitochondrial fractions, showed that binding reached a plateau between 7 min and 13 min, increasing thereafter. Binding was linear with fraction protein over a range of 200-415 micrograms/ml incubation medium. Binding was completely inhibited by glycine, alanine, alpha-aminobutyric acid, beta-aminoisobutyric acid, hypotaurine and strychnine, and to a lesser extent by 2,2-dimethyl-beta-alanine, brucine and gelsemine. It was insensitive to taurine, gamma-aminobutyric acid (GABA), 2-guanidinoethanesulfonic acid (GES), carnosine, and bicuculline methiodide. Binding was reversible, saturable (KD 20 microM), and heat sensitive.
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Affiliation(s)
- L M Orensanz
- Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain
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Horikoshi T, Asanuma A, Yanagisawa K, Anzai K, Goto S. Taurine and beta-alanine act on both GABA and glycine receptors in Xenopus oocyte injected with mouse brain messenger RNA. Brain Res 1988; 464:97-105. [PMID: 2464409 DOI: 10.1016/0169-328x(88)90002-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The responding pathway (process from agonist binding to channel opening) of taurine and beta-alanine was investigated in Xenopus oocytes injected with mouse brain poly(A)+ RNA. Responses to gamma-aminobutyric acid (GABA), glycine, taurine and beta-alanine were induced in oocytes injected with poly(A)+ RNA extracted from 3 regions, cerebrum, cerebellum and brainstem of the mouse brain. From comparison, responses to these 4 inhibitory amino acids in each regional poly(A)+ RNA-injected oocytes were categorized into at least 3 groups: (1) GABA, (2) glycine, and (3) taurine and beta-alanine. No cross-desensitization was observed between GABA response and glycine response, but taurine and beta-alanine responses cross-desensitized both the GABA and glycine responses. Taurine and beta-alanine responses were partially inhibited by the GABA antagonist, bicuculline, and also by the glycine antagonist, strychnine. The results suggest that the taurine or the beta-alanine response in the brain is caused through both the GABA receptor and the glycine receptor.
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Affiliation(s)
- T Horikoshi
- Department of Physiology, School of Dental Medicine, Tsurumi University, Yokohama, Japan
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47
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Aragón MC, Agulló L, Giménez C. Depolarization-induced release of glycine and beta-alanine from plasma membrane vesicles derived from rat brain synaptosomes. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 941:209-16. [PMID: 3132974 DOI: 10.1016/0005-2736(88)90181-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glycine and beta-alanine actively loaded into brain synaptic plasma membrane vesicles were released into the external medium by using the classical depolarization agents high K+ and veratridine. This release occurs via a Ca2+-independent process. Measurements of membrane depolarization using tetraphenylphosphonium uptake show a close correlation between changes in the membrane potential and stimulation of the efflux process. Results shown herein and previously reported by our group (Aragón, M.C. and Giménez, C. (1986) Biochim. Biophys. Acta 855, 257-264; Agulló, L., Jiménez, B., Aragón, M.C. and Giménez, C. (1986) Eur. J. Biochem. 159, 611-617), suggest that the glycine and beta-alanine transport systems in synaptic plasma membranes are susceptible of modulation by changes in ionic fluxes and hence in the membrane potential, similar to those occurring during depolarization and repolarization.
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Affiliation(s)
- M C Aragón
- Centre de Biologia Molecular, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
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48
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Abstract
In order to define which receptor-channel complexes are activated by beta-alanine, we performed cross-desensitization experiments between this amino acid and the classical inhibitory neurotransmitters, glycine and gamma-aminobutyric acid (GABA), all of which increase chloride conductances. Using the whole-cell patch-clamp technique and cultured chick spinal neurons, we found that beta-alanine completely desensitizes the glycine response, and only partially reduces GABA evoked currents. No interaction occurred between GABA and glycine at the level of their respective receptors. Conversely, both GABA and glycine reduced the beta-alanine response. These results indicate that beta-alanine activates the glycine receptor, and also suggest that it could be a partial agonist of GABAA receptor(s).
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Affiliation(s)
- D Choquet
- INSERM U 261, Département des Biotechnologies, Institut Pasteur, Paris, France
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49
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Sandberg M, Hagberg H, Jacobson I, Karlsson B, Lehmann A, Hamberger A. Analysis of amino acids: neurochemical application. Life Sci 1987; 41:829-32. [PMID: 2886876 DOI: 10.1016/0024-3205(87)90173-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
For high sensitivity analysis of neuroactive amino acids, liquid chromatography employing precolumn derivatisation with o-phthalaldehyde (OPA) is suitable for several reasons. The OPA reagent is non-fluorescent per se, the reaction occurs rapidly in alkaline aqueous solutions and forms highly fluorescent derivatives with primary amines.
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50
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Agullo L, Jimenez B, Aragón C, Giménez C. Beta-alanine transport in synaptic plasma membrane vesicles from rat brain. Efflux, exchange and stoichiometry. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 159:611-7. [PMID: 3093232 DOI: 10.1111/j.1432-1033.1986.tb09929.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The efflux and exchange of beta-alanine were studied in synaptic plasma membrane vesicles from rat brain. The mechanism of beta-alanine translocation has been probed by comparing the ion dependence of net efflux to that of exchange. Dilution-induced efflux requires the simultaneous presence of internal sodium and chloride ions while influx is dependent on the presence of these two ions on the outside [Zafra, F., Aragón, M. C., Valdivieso, F. and Giménez, C. (1984) Neurochem Res. 9, 695-707]. These data show that the release of beta-alanine occurs via the carrier system and that it is cotransported with sodium and chloride ions. beta-Alanine efflux from the membrane vesicles is stimulated by external beta-alanine. This exchange does not require external sodium and chloride but it is dependent on the external concentration of beta-alanine. Half-maximal stimulation is obtained at a beta-alanine concentration similar to the Km for beta-alanine influx. Results of the direct measurements of the coupling of sodium and chloride to the transport of beta-alanine by using a kinetic approach allow us to propose a stoichiometry for the translocation cycle catalyzed by the beta-alanine transporter of three sodium ions and one chloride ion per beta-alanine zwitterion. To account for all the observed effects of external ions, beta-alanine concentrations and membrane potential on beta-alanine influx and efflux, a kinetic model of the Na+/Cl-/beta-alanine cotransport system is discussed.
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