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:3.5.4.1 (cytosine deaminase)
747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytosine deaminase (EC 3.5.4.1) from Salmonella typhimurium has been purified 419-fold to apparent homogeneity. SDS polyacrylamide gel electrophoresis indicated that the final cytosine deaminase preparation was homogeneous. The molecular weight of cytosine deaminase was determined to be approx. 230000 containing four identical subunits with each subunit having a molecular weight 54000. Cytosine was deaminase has a pH optimum of 7.30 to 7.50 and a temperature optimum of 45 to 50 degrees C. Cytosine was deaminated specifically; 5-fluorocytosine was deaminated to a lesser extent. The Km and V values for cytosine were 0.74 mM and 47.16 mumole/min, respectively. As effectors of enzyme activity, PPi stimulated the deamination while metal ions and orotidine monophosphate inhibited it. The physical characteristics of cytosine deaminase lend credence to its proposed salvage role in pyrimidine metabolism as indicated previously by physiological studies (West, T.P. and O'Donovan, G.A., J. Bacteriol. (1982) 149, 1171-1174).
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PMID:Purification and some properties of cytosine deaminase from Salmonella typhimurium. 675 59

The synthesis of cytosine deaminase in Salmonella typhimurium is repressed by pyrimidines. This repression is mediated by both a uridine and a cytidine compound, indicating a distinct difference in the regulation of synthesis of cytosine deaminase from the regulation of the de novo pyrimidine pathway enzymes. A salvage role for the enzyme in pyrimidine metabolism is postulated.
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PMID:Repression of cytosine deaminase by pyrimidines in Salmonella typhimurium. 703 40

Pyrimidine synthesis in the food spoilage agent Burkholderia cepacia ATCC 25416 was investigated. The five de novo pathway enzymes of pyrimidine biosynthesis were found to be active in B. cepacia ATCC 25416 and growth of this strain on uracil had an effect on the de novo enzyme activities. The in vitro regulation of aspartate transcarbamoylase activity in B. cepacia ATCC 25416 was studies and its activity was inhibited by PP(i), ATP, GTP, CTP and UTP. The enzymes cytidine deaminase, uridine phosphorylase and cytosine deaminase were found to be active in the salvage of pyrimidines in ATCC 25416. Overall, de novo pyrimidine synthesis in B. cepacia ATCC 25416 was regulated at the level of enzyme activity and its pyrimidine salvage enzymes differed from those found in B. cepacia ATCC 17759.
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PMID:Pyrimidine synthesis in Burkholderia cepacia ATCC 25416. 757 30

Pyrimidine nucleoside catabolism in the human pathogen Sphingomonas paucimobilis was studied. It was observed that S. paucimobilis was only capable of utilizing cytidine or deoxycytidine as a sole nitrogen source when glucose served as the carbon source. Thinlayer chromatographic analyses of cytidine and uridine catabolic products revealed that the enzymes cytidine deaminase and uridine phosphorylase were active in the extracts prepared from S. paucimobilis cells. The levels of cytidine deaminase and cytosine deaminase activities were lowered after growth on cytidine or deoxycytidine as a nitrogen source instead of ammonium sulfate. Uridine phosphorylase activity increased more than 4-fold after growth on deoxycytidine as a nitrogen source while growth on the nitrogen source cytidine caused a depression in phosphorylase activity.
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PMID:Pyrimidine nucleoside catabolism in Sphingomonas paucimobilis: role of cytidine deaminase and uridine phosphorylase. 760 8

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

Pyrimidine ribonucleoside degradation in the human pathogen Pseudomonas aeruginosa ATCC 15692 was investigated. Either uracil, cytosine, 5-methylcytosine, thymine, uridine or cytidine supported P. aeruginosa growth as a nitrogen source when glucose served as the carbon source. Using thin-layer chromatographic analysis, the enzymes nucleoside hydrolase and cytosine deaminase were shown to be active in ATCC 15692. Compared to (NH4)2SO4-grown cells, nucleoside hydrolase activity in ATCC 15692 approximately doubled after growth on 5-methylcytosine as a nitrogen source while its cytosine deaminase activity increased several-fold after growth on the pyrimidine bases and ribonucleosides examined as nitrogen sources. Regulation at the level of protein synthesis by 5-methylcytosine was indicated for nucleoside hydrolase and cytosine deaminase in P. aeruginosa.
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PMID:Degradation of pyrimidine ribonucleosides by Pseudomonas aeruginosa. 883 31

By functional complementation of a fcy1 null mutant of Saccharomyces cerevisiae, we have cloned and characterized the FCY1 gene, encoding cytosine deaminase in Saccharomyces cerevisiae, and its homologue FCA1, encoding cytosine deaminase in Candida albicans. Disruption of FCY1 resulted in high resistance to 5-fluorocytosine (10(-2) M) and in total loss of cytosine deaminase activity. By contrast the transformation by FCY1 or FCA1 of the haploid FCY1-disrupted host strain restored sensitivity to 5-fluorocytosine and allowed growth on cytosine, as a source of pyrimidine, or ammonium. FCA1 as opposed to FCY1 contains an intron. FCA1 and FCY1 encode respectively 150- and 158- residue proteins of 60% identity. Both Fcy1p and Fca1p share common motifs with cytidine and CMP deaminases, but homology with cytosine deaminase of E. coli could not be detected.
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PMID:Characterization of the Saccharomyces cerevisiae FCY1 gene encoding cytosine deaminase and its homologue FCA1 of Candida albicans. 900 Mar 74

The effect of the aging on the activities of enzymes involved in UMP-CMP metabolism were evaluated in the heart of newborn (1-day-old), young (20-day-old), adult (12-month-old), and aged (30-month-old) chickens. In newborn animals, UMP metabolism proceeds preferentially towards cytidine compounds rather than to breakdown. In addition, two pathways different from those involved in de novo synthesis may contribute to the synthesis of UMP: one, through cytosine deaminase that shows its maximal activity; the other, by uridine kinase, the main "salvage" enzyme of pyrimidine nucleotides. In young chickens, pyrimidine metabolism regards especially UMP. In fact, the lower activities of cytidylate phosphatase and cytosine deaminase, together with the remarkable increase of uridine kinase indicate that the metabolic flux converges on the main salvage pathway. In adult chickens, pyrimidine catabolism is enhanced, as supported by the maximal activity of the enzymes involved in UMP-CMP breakdown. On the contrary, the remarkable reduction of the anabolic enzymes suggests a limited resort to the salvage pathways. Finally, in aged chickens a reduced pyrimidine catabolism and a greater utilization of the salvage pathways appear to take place, thus contributing to the maintenance of pyrimidine nucleotide pool.
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PMID:Influence of age on enzyme activities of pyrimidine metabolism in the chicken heart. 989 51

The E. coli cytosine deaminase (CD) provides a negative selection system for suicide gene therapy as CD transfectants are eliminated following 5-fluorocytosine (5FC) treatment. Here we report a positive selection system for the CD gene using 5-fluorouracil (5FU) and cytosine in selection medium to screen for CD-positive transfectants. It is based on the relief of 5FU toxicity by uracil which is converted from cytosine via CD catalysis, as uracil competes with the toxic 5FU in subsequent pyrimidine metabolism. Hence, a retroviral vector containing the CD gene may provide both positive and negative selections after gene transfer. The CD transfectants selected with the positive selection system showed susceptibility to 5FC in subsequent negative selection in vitro and in vivo. Therefore, this dual selection system is useful not only for combination therapy with transgene and CD gene, but can also act to eliminate selectively transduced cells after the transgene has furnished its effects or upon undesired conditions if 5FC is applied for negative selection in vivo.
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PMID:Provision of positive and negative selections in retroviral vectors containing the cytosine deaminase gene. 993 Mar 12

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


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