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

---

Query: EC:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new selective medium has been developed for cells containing the enzyme deoxycytidine deaminase. This medium contains hypoxanthine, aminopterin, and 5-methyldeoxycytidine (HAM medium). To survive in the presence of the aminopterin, the cells must utilize deoxycytidine deaminase to convert the 5-methyldeoxycytidine to thymidine. The cells must also have thymidine kinase and hypoxanthine phosphoribosyltransferase. A mouse cell line deficient in deoxycytidine deaminase has been isolated from a deoxycytidine kinase-deficient line, using 5-bromodeoxycytidine as the selective agent. A hybrid line between this double mutant and a human diploid fibroblast was isolated in HAM medium. The hybrid line contains the chromosomes expected of a human-mouse hybrid. The deoxycytidine deaminase isozyme patterns on cellogel show that the human-mouse hybrid cell line produces an enzyme with an electrophoretic mobility intermediate between that of the human and that of the mouse.
...
PMID:A human-mouse somatic hybrid line selected for human deoxycytidine deaminase. 123 1

Dialyzed extracts of Bacillus megaterium KM contain thymidine, deoxyadenosine, and deoxyguanosine kinase activities. Thymidine kinase activity is best with deoxyadenosine triphosphate or deoxyguanosine triphosphate (dGTP) as the phosphoryl donor, whereas the best deoxyadenosine kinase activity is obtained with dGTP or adenosine triphosphate. Deoxyguanosine kinase activity functions optimally with deoxycytidine triphosphate as the donor. Although the thymidine kinase activity of crude extracts does not have a demonstrable divalent cation requirement, the addition of Mg(2+) or Mn(2+) is necessary for the formation of thymidine di- and triphosphates. The synthesis of thymidine kinase appears to be partially derepressed by thymine starvation. Incubation of extracts with deoxyadenosine and dGTP results in the substantial accumulation of deoxyadenosine di- and triphosphates. Extracts deaminate deoxycytidine to deoxyuridine, presumably as a consequence of the action of deoxycytidine deaminase, and then convert deoxyuridine to deoxyuridylic acid. B. megaterium extracts do not contain any detectable deoxycytidine kinase activity.
...
PMID:Deoxynucleoside kinases of Bacillus megaterium KM. 499 37

The activities of the key enzymes of pyrimidine nucleotide and DNA syntheses in 43 human tumors and 28 normal human tissues were investigated. The activities of cytidine triphosphate synthetase, deoxycytidine monophosphate deaminase, uridine kinase, thymidine kinase, thymidine monophosphate kinase and DNA polymerase were markedly increased in tumor tissues, compared with those in the corresponding normal tissues, while the activities of deoxycytidine kinase, cytidine deaminase and deoxycytidine deaminase were only slightly increased. The use of thymidine and deoxyuridine as substrates of human pyrimidine nucleoside phosphorylase gave 1 to 2 orders of magnitude higher activity than that of uridine.
...
PMID:Activities of various enzymes of pyrimidine nucleotide and DNA syntheses in normal and neoplastic human tissues. 628 2

5-Methylcytosine ( 5MeCyt ) is a possible regulator of eukaryotic gene transcription. We investigated whether this compound could be introduced into DNA from exogenous deoxyribonucleoside 5-methyl-2'-deoxycytidine ( 5MedCyd ). High concentrations of 5MedCyd inhibited the growth of several types of human leukemic cell lines in vitro. However, the effect could be accounted for by dThd, a deamination product of 5MedCyd . We found that radioactivity from [methyl-14C] 5MedCyd and [2-14C] 5MedCyd was incorporated into DNA as thymidylate, and none was present as 5MeCyt . There are two conceivable metabolic pathways from 5MedCyd to thymidylate. The first consists of deoxycytidine or thymidine kinase and deoxycytidylate deaminase, and the second of sequential reactions catalyzed by deoxycytidine deaminase and thymidine kinase. No indication of the first pathway was demonstrable in human leukemic cells. We conclude that the DNA exclusion of 5MeCyt from exogenous 5MedCyd takes place because of powerful deoxycytidine deaminase activity in human malignant hematopoietic cells.
...
PMID:5-Methyl-2'-deoxycytidine. Metabolism and effects on cell lethality studied with human leukemic cells in vitro. 658 84

The present study was undertaken to assess the predictive value of pretherapeutic determinants of ara-C metabolism and proliferative activity of leukemic blasts for early response to antileukemic therapy in the setting of granulocyte-macrophage colony-stimulating factor (GM-CSF)-based priming before and during TAD-9 induction in 36 consecutive patients with de novo acute myeloid leukemia (AML). Ara-C metabolism was assessed by the activities of deoxycytidine kinase (DCK), deoxycytidine deaminase (DCD), DNA polymerase alpha (Poly alpha), and overall polymerase (overall Poly). The fraction of cells in S phase (%S phase) and thymidine kinase (TK) activity were determined as a measure of proliferative activity. Early response to therapy was defined by the percentage of leukemic blasts in the bone marrow 5 to 7 days after completion of TAD-9 with less than 5% signaling an adequate response and greater than 5% indicating an inadequate early reduction, respectively. While neither %S phase, DCK, nor overall Poly activity were predictive for early response, TK and Poly alpha activities were significantly higher for cases with adequate blast cell clearance. The respective median values were for TK 3.8 versus 1.85 pmol/min/mg protein (P = .012), and for Poly alpha 1.9 versus 0.69 pmol/min/mg protein (P = .014). An inverse relation was detected for DCD activity which was significantly lower in responding patients with a median of 0.33 nmol/min/mg protein (range, 0.0 to 29.5) as compared to a median of 5.1 nmol/min/mg protein (range, 0.11 to 8.45) in early nonresponders, (P = .009). Taking the respective median values as arbitrary cut-points for high or low enzyme activities, responders and nonresponders could be discriminated prospectively. Hence, 14 of 16 cases (88%) with DCD activities below the median of 1.56 nmol/min/mg protein responded as compared to only 3 of 14 (22%) patients with higher DCD activities (P = .0004). From the 15 patients with TK activity above the overall median of 3.2 pmol/min/mg protein, 11 cases (73%) achieved an adequate blast cell clearance while only 6 of 17 cases (35%) with lower values responded (P = .035). Similarly, 12 of 15 patients (80%) with high Poly alpha levels (>1.22 pmol/min/mg protein) responded to induction therapy as compared to only 5 of 14 patients (36%) with lower enzyme activities (P = .02). By logistic regression analysis of enzyme activities, DCD activity was found to be the most sensitive parameter to predict an adequate blast cell clearance (P = .032). Activities of DCD and TK were not only associated with initial response but were also found predictive for remission duration. Hence, from 11 patients with low TK levels 8 (73%) relapsed within 1 year, whereas only 2 of 11 (18%) patients with high TK activity experienced a recurrence of their disease (P = .015). Six of 9 (66%) patients with higher than median DCD levels relapsed within 1 year, whereas 10 of 14 patients (71%) with lower DCD levels had a longer remission duration (P = .085). Analysis of DCD gene expression at the mRNA level by a semi-quantitative reverse transcriptase-polymerase chain reaction method showed that a high transcription rate of the DCD gene was associated with high enzyme activities and vice versa. Hence, the observed intraindividual differences in DCD activity are a reflection of differences in gene activity and transcription rate rather than of variants in translation. Although further analyses are needed to elucidate the molecular mechanisms that determine the variation of enzyme activities in individual patients, the present study strongly suggests that pretherapeutic determination of TK and Poly alpha as well as of DCD allows to predict response to TAD-9 + GM-CSF induction therapy and may provide the means for the development of a risk adapted treatment strategy.
...
PMID:Activity of thymidine kinase and of polymerase alpha as well as activity and gene expression of deoxycytidine deaminase in leukemic blasts are correlated with clinical response in the setting of granulocyte-macrophage colony-stimulating factor-based priming before and during TAD-9 induction therapy in acute myeloid leukemia. 929 31

In order to obtain general metabolic profiles of pyrimidine ribo- and deoxyribonucleotides in potato (Solanum tuberosum L.) plants, the in situ metabolic fate of various (14)C-labelled precursors in disks from growing potato tubers was investigated. The activities of key enzymes in potato tuber extracts were also studied. The following results were obtained. Of the intermediates in de novo pyrimidine biosynthesis, [(14)C]carbamoylaspartate was converted to orotic acid and [2-(14)C]orotic acid was metabolized to nucleotides and RNA. UMP synthase, a bifunctional enzyme with activities of orotate phosphoribosyltransferase (EC 2.4.2.10) and orotidine 5'-monophosphate decarboxylase (EC 4.1.1.23), exhibited high activity. The rates of uptake of pyrimidine ribo- and deoxyribonucleosides by the disks were high, in the range 2.0-2.8 nmol (g FW)(-1) h(-1). The pyrimidine ribonucleosides, uridine and cytidine, were salvaged exclusively to nucleotides, by uridine/cytidine kinase (EC 2.7.1.48) and non-specific nucleoside phosphotransferase (EC 2.7.1.77). Cytidine was also salvaged after conversion to uridine by cytidine deaminase (EC 3.5.4.5) and the presence of this enzyme was demonstrated in cell-free tuber extracts. Deoxycytidine, a deoxyribonucleoside, was efficiently salvaged. Since deoxycytidine kinase (EC 2.7.1.74) activity was extremely low, non-specific nucleoside phosphotransferase (EC 2.7.1.77) probably participates in deoxycytidine salvage. Thymidine, which is another pyrimidine deoxyribonucleoside, was degraded and was not a good precursor for nucleotide synthesis. Virtually all the thymidine 5'-monophosphate synthesis from thymidine appeared to be catalyzed by phosphotransferase activity, since little thymidine kinase (EC 2.7.1.21) activity was detected. Of the pyrimidine bases, uracil, but not cytosine, was salvaged for nucleotide synthesis. Since uridine phosphorylase (EC 2.4.2.3) activity was not detected, uracil phosphoribosyltransferase (EC 2.4.2.9) seems to play the major role in uracil salvage. Uracil was degraded by the reductive pathway via beta-ureidopropionate, but cytosine was not degraded. The activities of the cytosine-metabolizing enzymes observed in other organisms, pyrimidine nucleoside phosphorylase (EC 2.4.2.2) and cytosine deaminase (EC 3.5.4.1), were not detected in potato tuber extracts. Operation of the de novo synthesis of deoxyribonucleotides via ribonucleotide reductase and of the salvage pathway of deoxycytidine was demonstrated via the incorporation of radioactivity from both [2-(14)C]cytidine and [2-(14)C]deoxycytidine into DNA. A novel pathway converting deoxycytidine to uracil nucleotides was found and deoxycytidine deaminase (EC 3.5.4.14), an enzyme that may participate in this pathway, was detected in the tuber extracts.
...
PMID:Profiles of pyrimidine biosynthesis, salvage and degradation in disks of potato (Solanum tuberosum L.) tubers. 1224 48

Using different 5-fluoropyrimidine analogues, positive selection procedures for obtaining mutants blocked in pyrimidine and purine salvage genes of Lactococcus lactis were established. Strains lacking the following enzyme activities due to mutations in the corresponding genes were isolated: uracil phosphoribosyltransferase (upp), uridine/cytidine kinase (udk), pyrimidine nucleoside phosphorylase (pdp), cytidine/deoxycytidine deaminase (dd),thymidine kinase (tdk) and purine nucleoside phosphorylase (pup). Based on an analysis of the mutants obtained, the pathways by which L. lactis metabolizes uracil and the different pyrimidine nucleosides were verified. The substrate specificities of the different enzymes were determined. It was demonstrated that a single pyrimidine nucleoside phosphorylase accounts for the phosphorolytical cleavage of uridine, deoxyuridine and thymidine, and a single purine nucleoside phosphorylase has activity towards both the ribonucleoside and deoxyribonucleoside derivatives of adenine, guanine and hypoxanthine. No phosphorylase activity towards xanthosine appeared to be present. The selection procedures developed during this work may be employed in establishing markers on the chromosome of many related lactic acid bacteria.
...
PMID:Powerful methods to establish chromosomal markers in Lactococcus lactis: an analysis of pyrimidine salvage pathway mutants obtained by positive selections. 2036 19

---