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)

Purine and pyrimidine enzyme profiles of human cell lines have been investigated. A novel observation was the finding that most of the cell lines showed very low or undetectable levels of cytidine (deoxycytidine) deaminase, while they possessed pyrimidine 5'-nucleotidase, cytidine and deoxycytidine kinase activities. Most cell lines showed high levels of adenosine deaminase and purine nucleoside phosphorylase activities and low levels of purine 5'-nucleotidase. We propose that high adenosine deaminase and purine nucleoside phosphorylase activities and low cytidine deaminase activity may be of importance for immature hematopoietic cells in order to ensure a balanced synthesis of the DNA precursors.
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PMID:Low cytidine deaminase levels in human hematopoietic cell lines. 362 11

Purine nucleotides are formed de novo by a widespread biochemical route that may be of monophyletic origin, or are synthesized from preformed purine bases and nucleosides through different salvage pathways. Three monophyletic sets of purine salvage enzymes, each of which catalyzes mechanistically similar reactions, can be identified: (a) adenine-, xanthine-, hypoxanthine- and guanine-phosphoribosyltransferases, which are all homologous among themselves, as well as to nucleoside phosphorylases; (b) adenine deaminase, adenosine deaminase, and adenosine monophophate deaminase; and (c) guanine reductase and inosine monophosphate dehydrogenase. These homologies support the idea that substrate specificity is the outcome of gene duplication, and that the purine nucleotide salvage pathways were assembled by a patchwork process that probably took place before the divergence of the three cell domains (Bacteria, Archaea, and Eucarya). Based on the ability of adenine PRTase to catalyze the condensation of PRPP with 4-aminoimidazole-5-carboxamide (AICA), a simpler scheme of purine nucleotide biosynthesis is presented. This hypothetical route requires the prior evolution of PRPP biosynthesis. Since it has been argued that PRPP, nucleosides, and nucleotides are susceptible to hydrolysis, they are very unlikely prebiotic compounds. If this is the case, it implies that many purine salvage pathways appeared only after the evolution of phosphorylated sugar biosynthetic pathways made ribosides available.
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PMID:The role of gene duplication in the evolution of purine nucleotide salvage pathways. 974 28

Purine metabolism plays a major role in regulating the availability of purine nucleotides destined for nucleic acid synthesis. Allantoate amidohydrolase catalyzes the conversion of allantoate to (S)-ureidoglycolate, one of the crucial alternate steps in purine metabolism. The crystal structure of a ternary complex of allantoate amidohydrolase with its substrate allantoate and an allosteric effector, a sulfate ion, from Escherichia coli was determined to understand better the catalytic mechanism and substrate specificity. The 2.25 A resolution X-ray structure reveals an alpha/beta scaffold akin to zinc exopeptidases of the peptidase M20 family and lacks the (beta/alpha)(8)-barrel fold characteristic of the amidohydrolases. Arrangement of the substrate and the two co-catalytic zinc ions at the active site governs catalytic specificity for hydrolysis of N-carbamyl versus the peptide bond in exopeptidases. In its crystalline form, allantoate amidohydrolase adopts a relatively open conformation. However, structural analysis reveals the possibility of a significant movement of domains via rotation about two hinge regions upon allosteric effector and substrate binding resulting in a closed catalytically competent conformation by bringing the substrate allantoate closer to co-catalytic zinc ions. Two cis-prolyl peptide bonds found on either side of the dimerization domain in close proximity to the substrate and ligand-binding sites may be involved in protein folding and in preserving the integrity of the catalytic site.
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PMID:Structural analysis of a ternary complex of allantoate amidohydrolase from Escherichia coli reveals its mechanics. 1736 92

Purine nucleotide catabolism is common to most organisms and involves a guanine deaminase to convert guanine to xanthine in animals, invertebrates, and microorganisms. Using metabolomic analysis of mutants, we demonstrate that Arabidopsis thaliana uses an alternative catabolic route employing a highly specific guanosine deaminase (GSDA) not reported from any organism so far. The enzyme is ubiquitously expressed and deaminates exclusively guanosine and 2'-deoxyguanosine but no other aminated purines, pyrimidines, or pterines. GSDA belongs to the cytidine/deoxycytidylate deaminase family of proteins together with a deaminase involved in riboflavin biosynthesis, the chloroplastic tRNA adenosine deaminase Arg and a predicted tRNA-specific adenosine deaminase 2 in A. thaliana. GSDA is conserved in plants, including the moss Physcomitrella patens, but is absent in the algae and outside the plant kingdom. Our data show that xanthosine is exclusively generated through the deamination of guanosine by GSDA in A. thaliana, excluding other possible sources like the dephosphorylation of xanthosine monophosphate. Like the nucleoside hydrolases NUCLEOSIDE HYDROLASE1 (NSH1) and NSH2, GSDA is located in the cytosol, indicating that GMP catabolism to xanthine proceeds in a mostly cytosolic pathway via guanosine and xanthosine. Possible implications for the biosynthetic route of purine alkaloids (caffeine and theobromine) and ureides in other plants are discussed.
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PMID:Plant purine nucleoside catabolism employs a guanosine deaminase required for the generation of xanthosine in Arabidopsis. 2413 Jan 59