Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.5.1.4 (deaminase)
5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyrimidine salvage enzyme activities in cell-free extracts of Toxoplasma gondii were assayed in order to determine which of these enzyme activities are present in these parasites. Enzyme activities that were detected included phosphoribosyltransferase activity towards uracil (but not cytosine or thymine), nucleoside phosphorylase activity towards uridine, deoxyuridine and thymidine (but not cytidine or deoxycytidine), deaminase activity towards cytidine and deoxycytidine (but not cytosine, cytidine 5'-monophosphate or deoxycytidine 5'-monophosphate), and nucleoside 5'-monophosphate phosphohydrolase activity towards all nucleotides tested. No nucleoside kinase or phosphotransferase activity was detected, indicating that T. gondii lack the ability to directly phosphorylate nucleosides. Toxoplasma gondii appear to have a single non-specific uridine phosphorylase enzyme which can catalyze the reversible phosphorolysis of uridine, deoxyuridine and thymidine, and a single cytidine deaminase activity which can deaminate both cytidine and deoxycytidine. These results indicate that pyrimidine salvage in T. gondii probably occurs via the following reactions: cytidine and deoxycytidine are deaminated by cytidine deaminase to uridine and deoxyuridine, respectively; uridine and deoxyuridine are cleaved to uracil by uridine phosphorylase; and uracil is metabolized to uridine 5'-monophosphate by uracil phosphoribosyltransferase. Thus, uridine 5'-monophosphate is the end-product of both de novo pyrimidine biosynthesis and pyrimidine salvage in T. gondii.
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PMID:Pyrimidine salvage pathways in Toxoplasma gondii. 845

N-Carbamoyl-D-amino acid amidohydrolase was purified 119-fold, with 36% overall recovery from a cell-free extract of Comamonas sp. E222c. The purified enzyme was homogeneous as judged by SDS/PAGE. The relative molecular mass of the native enzyme was 120,000 and that of the subunit was 40,000. The purified enzyme hydrolyzed various N-carbamoyl-D-amino acids to D-amino acids, ammonia and carbon dioxide. N-Carbamoyl-D-amino acids having hydrophobic groups served as good substrates for the enzyme. The Km and Vmax values for N-carbamoyl-D-phenylalanine were 19.7 mM and 13.1 units/mg, respectively, and those for N-carbamoyl-D-p-hydroxyphenylglycine were 13.1 mM and 0.56 units/mg, respectively. The enzyme strictly recognized the configuration of the substrate and only the D-enantiomer of the N-carbamoyl amino acid was hydrolyzed. The enzyme activity was not significantly affected by N-carbamoyl-L-amino acids and ammonia. The enzyme was sensitive to thiol reagents and did not require metal ions for its activity. The enzyme did not hydrolyze N-carbamoyl-beta-alanine or N-carbamoyl-DL-aspartate suggesting that the enzyme is different from the N-carbamoylamide-hydrolyzing enzymes involved in the pyrimidine degradation pathway. The enzyme did not hydrolyze allantoin and allantoic acid, which are intermediates in purine degradation, N-carbamoylsarcosine and citrulline, suggesting that it is a novel N-carbamoylamide amidohydrolase.
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PMID:N-carbamoyl-D-amino acid amidohydrolase from Comamonas sp. E222c purification and characterization. 846 43

The 2'-deoxy (2a) and 2'-ara-fluoro (3a) derivatives of zebularine [1-(beta-D-ribofuranosyl)-dihydropyrimidin-2-one, 1a] were phosphorylated in high yield to the 5'-nucleotides 2b and 3b, respectively, and characterized by HPLC, enzyme degradation, 1H, 13C and 31P NMR, and high resolution mass spectral analysis. Their inhibitory activity against partially purified MOLT-4 deoxycytidylate deaminase (dCMPD) in the presence of the allosteric effector deoxycytidine triphosphate (dCTP) and Mg+2 ion was examined. Compounds 2b and 3b inhibited dCMPD with Ki values of 2.1 x 10(-8) M and 1.2 x 10(-8) M, respectively. The parent nucleotide, zebularine monophosphate 1b was ineffective at concentrations > 100 mumol. The effect of the nucleosides, 1a-3a, as well as tetrahydrouridine (THU) and 2'-deoxy THU (dTHU), on the cellular production of DNA precursors was examined in human MOLT-4 peripheral lymphoblasts. It was shown that 1a, 2a and 3a all elevated intracellular dCTP and TTP levels in whole cells with the most powerful effect elicited by 1a. The 2'-fluoro derivative 3a was chemically phosphorylated much more cleanly and higher yield than 2a, without the formation of diphosphorylated by-products. This compound was found to be infinitely less sensitive to acid-catalyzed degradation than 2a. Since the substitution of fluorine for hydrogen had a slight potentiating effect on the dCMPD inhibitory activity while stabilizing the compound toward acid-catalyzed and enzymatic depyrimidination, compound 3b emerges as a very attractive tool for the pharmacological modulation of pyrimidine deaminase activity.
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PMID:Improved synthesis of zebularine [1-(beta-D-ribofuranosyl)-dihydropyrimidin-2-one] nucleotides as inhibitors of human deoxycytidylate deaminase. 858 52

Cytosine deaminase (EC 3.5.4.1), a non-mammalian enzyme, catalyzes the deamination of cytosine and 5-fluorocytosine to form uracil and 5-fluorouracil, respectively. Eukaryotic cells have been genetically modified with a bacterial cytosine deaminase gene to express a functional enzyme. When the genetically modified cells are combined with 5-fluorocytosine, it creates a potent negative selection system, which may have important applications in cancer gene therapy. In this paper, we introduce a novel positive selection method based upon the expression of the cytosine deaminase gene. This method utilizes inhibitors in the pyrimidine de novo synthesis pathway to create a condition in which cells are dependent on the conversion of pyrimidine supplements to uracil by cytosine deaminase. Thus, only cells expressing the cytosine deaminase gene can be rescued in a positive selection medium.
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PMID:Cytosine deaminase gene as a positive selection marker. 863 98

A determination of the possible role of the salvage enzyme cytosine deaminase or beta-alanine-pyruvate transaminase in the catabolism of the pyrimidine bases uracil and thymine by the opportunistic pathogen Burkholderia cepacia ATCC 25416 was undertaken. It was of interest to learn whether these enzymes were influenced by cell growth on pyrimidine bases and their respective catabolic products to the same degree as the pyrimidine reductive catabolic enzymes were. It was found that cytosine deaminase activity was influenced very little by cell growth on the pyrimidines tested. Using glucose as the carbon source, only B. cepacia growth on 5-methylcytosine as a nitrogen source increased deaminase activity by about three-fold relative to (NH4)2SO4-grown cells. In contrast, the activity of beta-alanine-pyruvate transaminase was observed to be at least double in glucose-grown ATCC 25416 cells when pyrimidine bases and catabolic products served as nitrogen sources instead of (NH4)2SO4. Transaminase activity in the B. cepacia glucose-grown cells was maximal after the strain was grown on either uracil or 5-methylcytosine as a nitrogen source compared to (NH4)2SO4-grown cells. A possible role for beta-alanine-pyruvate transaminase in pyrimidine base catabolism by B. cepacia would seem to be suggested from the similarity in how its enzyme activity responded to cell growth on pyrimidine bases and catabolic products when compared to the response of the three reductive catabolic enzymes.
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PMID:Role of cytosine deaminase and beta-alanine-pyruvate transaminase in pyrimidine base catabolism by Burkholderia cepacia. 1069 71

A superfamily of cyclic amidohydrolases, including dihydropyrimidinase, allantoinase, hydantoinase, and dihydroorotase, all of which are involved in the metabolism of purine and pyrimidine rings, was recently proposed based on the rigidly conserved structural domains in identical positions of the related enzymes. With these conserved domains, two putative cyclic amidohydrolase genes from Escherichia coli, flanked by related genes, were identified and characterized. From the genome sequence of E. coli, the allB gene and a putative open reading frame, tentatively designated as a hyuA (for hydantoin-utilizing enzyme) gene, were predicted to express hydrolases. In contrast to allB, high-level expression of hyuA in E. coli of a single protein was unsuccessful even under various induction conditions. We expressed HyuA as a maltose binding protein fusion protein and AllB in its native form and then purified each of them by conventional procedures. allB was found to encode a tetrameric allantoinase (453 amino acids) which specifically hydrolyzes the purine metabolite allantoin to allantoic acid. Another open reading frame, hyuA, located near 64.4 min on the physical map and known as a UUG start, coded for D-stereospecific phenylhydantoinase (465 amino acids) which is a homotetramer. As a novel enzyme belonging to a cyclic amidohydrolase superfamily, E. coli phenylhydantoinase exhibited a distinct activity toward the hydantoin derivative with an aromatic side chain at the 5' position but did not readily hydrolyze the simple cyclic ureides. The deduced amino acid sequence of the novel phenylhydantoinase shared a significant homology (>45%) with those of allantoinase and dihydropyrimidinase, but its functional role still remains to be elucidated. Despite the unclear physiological function of HyuA, its presence, along with the allantoin-utilizing AllB, strongly suggested that the cyclic ureides might be utilized as nutrient sources in E. coli.
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PMID:Functional expression and characterization of the two cyclic amidohydrolase enzymes, allantoinase and a novel phenylhydantoinase, from Escherichia coli. 1109 64

The vertebrate CRMP (collapsin-response-mediator protein) gene family comprises at least four members. These CRMPs exhibit about 60% amino acid identity with vertebrate dihydropyrimidinase (DHP), an amidohydrolase involved in the pyrimidine degradation pathway. CRMP is also referred to as DRP (DHP-related protein), TOAD-64 (turned on after division, 64 kDa) and Ulip (Unc-33-like phosphoprotein). These vertebrate CRMPs are expressed mainly in early neuronal differentiation, which suggests that they play a role in neuronal development. In this study we isolated two cDNA clones from nematode C. elegans based on their sequence homology to vertebrate CRMPs and DHP. These two molecules, termed CeCRMP/DHP-1 and -2, turned out to be Ulip-B and -A, respectively, which were previously identified in the C. elegans genomic database by Byk et al. (1998). These newly isolated molecules were believed to represent a common ancestral state before the gene duplication between CRMPs and DHP. CeCRMP/DHP-1 and -2 protein retained all putative zinc-binding residues thought to be essential for the amidohydrolase activity of DHP and exhibited a weak amidohydrolase activity when 5-bromo-dihydrouracil was used as a substrate. Whole-mount in situ hybridization and expression analysis using GFP fusions revealed that CeCRMP/DHP-1 was transiently expressed in the hypodermis of C. elegans during the early larva stage. CeCRMP/DHP-1 was also expressed in a single nerve cell between the pharynx and ring neuropil. On the other hand, expression of CeCRMP/DHP-2 was observed in the body wall muscle throughout the lifespan of C. elegans. These results indicate that a major site of CeCRMP/DHP-1 and -2 expression is non-neuronal. Targeted gene disruption of CeCRMP/DHP-2 caused no particular difference in appearance or movement phenotype.
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PMID:Cloning and characterization of the Caenorhabditis elegans CeCRMP/DHP-1 and -2; common ancestors of CRMP and dihydropyrimidinase? 1116 13

The cyclic amidohydrolase family enzymes, including hydantoinase, dihydropyrimidinase, allantoinase and dihydroorotase, are metal-dependent hydrolases and play a crucial role in the metabolism of purine and pyrimidine in prokaryotic and eukaryotic cells. With the increasing demand for the elucidation of enzyme structures and functions, along with industrial applications, the research on the family enzymes has recently been proliferating, but the related enzymes had been purified conventionally by multistep purification procedures. Here, we reported the expression in Escherichia coli cells of maltose-binding protein-fused family enzymes and their one-step purification. The expression levels of the fusion proteins account for 20-35% of the total protein in E. coli, allowing approximately 2-3 mg of the purified proteins by affinity chromatography to be obtained per 0.3 L of bacterial culture. As more promising results, their nascent biochemical properties, after the cleavage of the fusion proteins with Factor Xa, in terms of oligomeric structure, optimal pH, specific activity, and kinetic property, were also conserved as those from the native enzymes. The availability of the family enzymes to fusion strategy shows potential as a convenient procedure to recombinant protein purification and accelerates the structure-function study of the related family enzymes.
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PMID:High-level expression and one-step purification of cyclic amidohydrolase family enzymes. 1157 Aug 54

Cytosine deaminase (CD) is found in prokaryotes and fungi (but not higher eukaryotes) and catalyzes the deamination of cytosine and 5-fluorocytosine to uracil and 5-fluorouracil, respectively. The former activity is an important function within the pyrimidine-salvage pathway, while the latter activity allows the formation of a cytotoxic chemotherapeutic agent from a non-cytotoxic precursor. Recombinant bacterial CD from Escherichia coli has been subcloned, overexpressed, purified and crystallized for structural analysis. The crystals belong to space group R32, with unit-cell parameters a = b = 109.1, c = 240 A and diffract to at least 1.5 A resolution at a synchrotron X-ray source. There is one enzyme subunit per asymmetric unit and the Matthews coefficient V(M) is 2.8 A(3) Da(-1), corresponding to a solvent content of 56%. Selenomethionine-containing protein has been prepared and crystallized for MAD phasing.
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PMID:Crystallization and preliminary X-ray analysis of bacterial cytosine deaminase. 1167 31

Barbiturase, which catalyzes the reversible amidohydrolysis of barbituric acid to ureidomalonic acid in the second step of oxidative pyrimidine degradation, was purified to homogeneity from Rhodococcus erythropolis JCM 3132. The characteristics and gene organization of barbiturase suggested that it is a novel zinc-containing amidohydrolase that should be grouped into a new family of the amidohydrolases superfamily. The amino acid sequence of barbiturase exhibited 48% identity with that of herbicide atrazine-decomposing cyanuric acid amidohydrolase but exhibited no significant homology to other proteins, indicating that cyanuric acid amidohydrolase may have evolved from barbiturase. A putative uracil phosphoribosyltransferase gene was found upstream of the barbiturase gene, suggesting mutual interaction between pyrimidine biosynthesis and oxidative degradation. Metal analysis with an inductively coupled radiofrequency plasma spectrophotometer revealed that barbiturase contains approximately 4.4 mol of zinc per mol of enzyme. The homotetrameric enzyme had K(m) and V(max) values of 1.0 mm and 2.5 micromol/min/mg of protein, respectively, for barbituric acid. The enzyme specifically acted on barbituric acid, and dihydro-l-orotate, alloxan, and cyanuric acid competitively inhibited its activity. The full-length gene encoding the barbiturase (bar) was cloned and overexpressed in Escherichia coli. The kinetic parameters and physicochemical properties of the cloned enzyme were apparently similar to those of the wild-type.
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PMID:Barbiturase, a novel zinc-containing amidohydrolase involved in oxidative pyrimidine metabolism. 1174 40


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