Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.1.4 (deaminase)
 5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a Salmonella typhimurium strain made diploid for the thy region by introduction of the Escherichia coli episome, F'15, mutants resistant to trimethoprim in the presence of thymidine were selected. One was shown to be defective in deoxyuridine 5'-phosphate (dUMP) synthesis; it requires deoxyuridine or thymidine for growth and is sensitive to trimethoprim in the presence of deoxyuridine. Genetic studies showed that the mutant is mutated in two genes, dcd and dum, located at 70 and 18 min, respectively, on the Salmonella linkage map. The dcd gene cotransduces 95% with udk, the structural gene for uridine kinase. Both mutations are necessary to create a deoxyuridine requirement, providing evidence for the existence of two independent pathways for dUMP synthesis. Pool studies showed that a dum mutation by itself causes a small decrease in the deoxythymidine 5'-triphosphate (dTTP) pool of the cells, whereas a dcd mutation results in a much more marked decrease. The double mutant dcd dum, when incubated in the absence of deoxyuridine, contains barely detectable levels of dTTP. Enzyme analysis revealed that dcd encodes deoxycytidine 5'-triphosphate deaminase. The gene product of the dum gene has not yet been identified; it does not encode either subunit of ribonucleoside diphosphate reductase or deoxyuridine 5'-triphosphate pyrophosphatase. Mutants deleted for the dcd-udk region of the S. typhimurium chromosome were isolated.
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PMID:Thymidine-requiring mutants of Salmonella typhimurium that are defective in deoxyuridine 5'-phosphate synthesis. 31 43

The metabolism of deoxycytidine (dCyd) and dCyd nucleotides in Yoshida ascites sarcoma (YS) cells and the host rat liver was investigated with reference to the increased excretion of urinary dCyd. Incorporation of [14C]orotic acid into the livers of rats at the fifth day after the transplantation of YS cells, the time when the amount of excretion of dCyd in urine was near maximal, was 2 times higher than that into the normal rat livers. After the injection of [14C]orotic acid, the ratio of the specific radioactivity of cytidylate to uridylate moieties of the host liver RNA was measured and found to be higher than that of normal rat liver RNA and to be similar to that of YS cell RNA. When [14C]orotic acid was injected into rats followed by the transplantation of YS cells, the radioactivities present in the livers disappeared more rapidly than those in the control rat livers. The activities of pyrimidine de novo synthesis enzymes, such as cytidine triphosphate synthetase (EC 6.3.4.2) and cytidine diphosphate reductase (EC 1.17.4.1), in YS were higher than those in both rat ascites hepatoma AH 7974 and Walker 256 carcinosarcoma, the transplantations of which did not induce increased excretion of dCyd into urine of the hosts. The activities of dCyd kinase (EC 2.7.1.10) and dCyd deaminase (EC 3.5.4.5) in YS cells were lower than those in the other two tumors investigated. The activities of cytidine triphosphate synthetase and cytidine diphosphate reductase in the livers of YS-bearing rats were elevated compared with those in the livers of rat ascites hepatoma AH 7974- or Walker 256 carcinosarcoma-bearing rats and normal rats, while the activities of dCyd kinase, 5'-nucleotidase (EC 3.1.3.5), and dCyd deaminase were similar between normal rat livers and tumor-bearing rat livers. These results suggest that the increased excretion of urinary dCyd in YS-bearing rats could be caused by both the stimulation of the synthesis of dCyd nucleotides and the low activity of dCyd deaminase in YS cells as well as in the host liver.
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PMID:Origin of increased deoxycytidine excretion into urine of rats bearing Yoshida ascites sarcoma. 672 78

Thymidine triphosphate, a negative regulator of deoxycytidylate deaminase, was found to bind covalently to this enzyme on exposure to UV light at 254 nM. The rate of half-maximal fixation was extremely rapid, occurring within 30 s and probably attaining a maximum of about 1 mol of dTTP fixed/mol of enzyme subunit. In contrast to the case of ribonucleotide reductase (Ericksson, S., Caras, I. W., and Martin, D. W., Jr. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 81-85) where the fixation of dTTP inactivated this enzyme, the activity of the deaminase was unaffected. The bound nucleotide could be released on exposure to UV 254 nm light in the presence of dCTP or dTTP but not dATP or dGTP. The enzyme-fixed nucleotide was found to remain with the larger of the two peptides released as a result of CNBr treatment of the labeled enzyme. Studies are in progress to define the location of this nucleotide, which will be aided greatly by our recent clarification of the complete amino acid sequence of T2-deoxycytidylate deaminase.
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PMID:Studies on identifying the allosteric binding sites of deoxycytidylate deaminase. 674 49

Recent studies of in vitro DNA synthesis have shown that fidelity of replication is influenced by the relative concentrations of deoxyribonucleoside triphosphates (dNTPs). Several investigators have used reconstituted prokaryotic replication systems to copy defined natural templates and have shown that specific incorporation errors can be induced by an appropriate bias of the precursor pools. The recent demonstration of mutator phenotypes among mutant Chinese hamster ovary cell lines with altered intracellular dNTP pools has allowed extension of the in vitro observations to eukaryotic replication and repair mechanisms. We describe here three mutant murine T-lymphosarcoma cell lines with altered dNTP pools and increased rates of spontaneous mutation to dexamethasone resistance and 6-thioguanine resistance. Unlike previously described mammalian cells with mutator phenotypes, these three lines have demonstrable defects in known structural gene products. Two of these cell lines are heterozygous for mutations affecting the M1 subunit of ribonucleoside diphosphate reductase; the other mutant is deficient in deoxycytidylate deaminase. In each cell line these mutations result in deranged endogenous dNTP pools and increased rates of spontaneous mutation, which are shown to be characteristic of the cell line and independent of the two genetic markers examined. Furthermore, normalization of the dNTP pools of the deaminase-deficient cells suppresses its mutator phenotype. Thus, abnormal dNTP pools seem to cause enhanced mutagenesis in mammalian cells.
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PMID:Mutator phenotypes in mammalian cell mutants with distinct biochemical defects and abnormal deoxyribonucleoside triphosphate pools. 701 32

Gemcitabine is a deoxycytidine (dCyd) analogue with activity against several solid cancers. Gemcitabine is activated by dCyd kinase (dCK) and interferes, as its triphosphate dFdCTP, with tumor growth through incorporation into DNA. Alternatively, the metabolite gemcitabine diphosphate (dFdCDP) can interfere with DNA synthesis and thus tumor growth through inhibition of ribonucleotide reductase. Gemcitabine can be inactivated by the enzyme dCyd deaminase (dCDA). In most in vitro models, resistance to gemcitabine was associated with a decreased dCK activity. In all these models, resistance was established using continuous exposure to gemcitabine with increasing concentrations; however, these in vitro models have limited clinical relevance. To develop in vivo resistance to gemcitabine, we treated mice bearing a moderately sensitive tumor Colon 26-A (T/C = 0.25) with a clinically relevant schedule (120 mg/kg every 3 days). By repeated transplant of the most resistant tumor and continuation of gemcitabine treatment for >1 year, the completely resistant tumor Colon 26-G (T/C = 0.96) was created. Initial studies focused on resistance mechanisms known from in vitro studies. In Colon 26-G, dCK activity was 1.7-fold decreased; dCDA and DNA polymerase were not changed; and Colon 26-G accumulated 1.5-fold less dFdCTP, 6 hours after a gemcitabine injection, than the parental tumor. Based on in vitro studies, these relative minor changes were considered insufficient to explain the completely resistant phenotype. Therefore, an expression microarray was done with Colon 26-A versus Colon 26-G. Using independently grown nonresistant and resistant tumors, a striking increase in expression of the RRM1 subunit gene was found in Colon 26-G. The expression of RRM1 mRNA was 25-fold increased in the resistant tumor, as measured by real-time PCR, which was confirmed by Western blotting. In contrast, RRM2 mRNA was 2-fold decreased. However, ribonucleotide reductase enzyme activity was only moderately increased in Colon 26-G. In conclusion, this is the first model with in vivo induced resistance to gemcitabine. In contrast to most in vitro studies, dCK activity was not the most important determinant of gemcitabine resistance. Expression microarray identified RRM1 as the gene with the highest increase in expression in the Colon 26-G, which might clarify its complete gemcitabine-resistant phenotype. This study is the first in vivo evidence for a key role for RRM1 in acquired gemcitabine resistance.
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PMID:In vivo induction of resistance to gemcitabine results in increased expression of ribonucleotide reductase subunit M1 as the major determinant. 1623 Apr 16