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Results for “Nucleoside-Phosphate Kinase”

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At least 19 recordsLinked to original sources
PubMed1976

[Effect of alkylating chemical substances on the activity and molecular heterogeneity of mouse sarcoma 180 nucleoside phosphate kinases].

The fractionation of extracts from sarcoma 180 cells was carried out on DEAE-cellulose following the administration to tumor-bearing mice of one of chloroctyl amino-phenildioxan derivatives. The tumor regression was noted more than in 50 per cent. It was found that the tumor regression, caused by this alkylating agent, results in marked changes in the fractionation pattern of thymidilatkinases. The origin of these changes is being discussed.

Alkylating Agents↗
PubMed1978

Effects of 5-aza-2'-deoxycytidine on DNA synthesis in mouse lymphatic tissues.

5-Aza-2'-deoxycytidine-3H administered i. p. to mice is preferentially incorporated into nucleic acids in the spleen and thymus. The labeling of the spleen is maximal during first hours after drug administration and decreases rapidly thereafter. Following administration, 5-aza-2'-deoxycytidine is metabolized giving rise to several new compounds. The incorporation of 5-aza-2'-deoxycytidine is blocked by the simultaneously administered deoxycytidine to a lesser degree than that of deoxycytidine by the analogue. Maximal inhibition of deoxycytidine incorporation by the drug was observed in the spleen; the incorporation of thymidine under similar conditions was diminished only about 20%. However, pretreatment of the animals with the analogue resulted in a strong inhibition of thymidine incorporation (about 80%) both in the spleen and the thymus. Simultaneously the activity of thymidine and thymidylate kinases in cell-free spleen extracts was markedly depressed.

Animals↗
PubMed1976

Photochemical studies and ultraviolet sensitization of Escherichia coli thymidylate kinase by various halogenated substrate analogs.

The effect of 5-iodo-2'-deoxyuridine monophosphate (IdUMP), various 5-halogenated-5'-azido-2', 5' -dideoxyuridine derivatives, 2'-deoxy-6-azauridine (AzdUrd), and its halogenated analogs on the ultraviolet sensitization of Escherichia coli thymidylate kinase has been investigated. Only those compounds iodinated in position 5 enhance the rate of ultraviolet inactivation of this enzyme. However, 5'-azido nucleosides with iodo, bromo, chloro, or fluoro substituents in position 5 neither protect nor sensitize thymidylate kinase to ultraviolet inactivation. Thymidine 5'-monophosphate partially protects the enzyme against ultraviolet inactivation either in the presence or absence of ultraviolet-sensitizing iodinated analogs. Magnesium ion does not enhance the ultraviolet inactivation of thymidylate kinase by 5-iodinated nucleoside analogs. The kinatic data support an active site-directed enhancement of the enzyme to ultraviolet inactivation by 5-iodo-2'-deoxyuridine monophosphate, since the concentration of IdUMP required to attain 50% maximal enhancement is 0.24 mM which is in good agreement with its Ki of 0.18 mM. When either [125I]IdUMP or [2-14C]IdUMP was irradiated with the enzyme, both radioactivities were associated with the enzyme, however only with the 14C analog was the amount bound at half-saturation essentially equal to the amount required to inactivate the enzyme by 50%. These data support the hypothesis that the active entity in the enhancement by IdUMP of thymidylate kinase inactivation during ultraviolet irradiation is the uridylate free radical which is formed photochemically from IdUMP. Photochemical studies of 6-azauracil (AzUra), 2'-deoxy-6-azauridine, and 5-iodo-2'-deoxy-6-azauridine (IAzdUrd) were performed. Photolysis of IAzdUrd in the presence of a hydrogen donor yields AzdUrd which upon further photolysis yields the photohydrate. The photohydrate of AzdUrd when incubated in the dark at pH 5.2 is 90% converted back to AzdUrd, whereas the photohydrate of AzUra is only partially (20%) converted to AzUra. The rate of deiodination of IAzdUrd is 2.1-fold greater than that of IdUMP. Although the Ki of IdUMP and IAzdUrd is similar, the increased photosensitivity of the aza analog accounts for the much greater enhancement of ultraviolet inactivation of thymidylate kinase. The ability of a compound to enhance the ultraviolet inactivation of deoxythymidylate kinase is correlated with the potential of the compound to produce a free radical rather than a photohydrate when the enzyme-substrate analog complex is irradiated.

Escherichia coli↗
PubMed1977

An investigation of the homology of guanylate kinase isozymes in mammals and further evidence for multiple GUK gene loci.

Guanylate kinase in the red cells of 63 different mammalian species was studied by electrophoresis and multiple molecular forms of the enzyme were found in all species. Two species were investigated in more detail. Using molecular weight estimates as a criterion of homology, the fallow deer and the Chinese hamster were found to have isozymes that corresponded to isozyme e, f, and g of man. Variation in the guanylate kinase isozymes was detected in a small population of orangutans. Results suggested that isozymes a and b were monomeric and that they were the products of a gene locus, GUK1, different from the locus GUK3 which coded for isozymes e, f, and g. Products c and d of the presumptive GUK2 locus were not found in the orangutan.

Animals↗
PubMed1977

Characterization of pyrimidine nucleoside monophosphokinase in normal and malignant tissues.

It was found that there are two kinds of pyrimidine nucleoside, monophosphokinase deoxythymidine 5'-monophosphate-deoxyuridine 5'-monophosphate (dTMP-dUMP) kinase and cytidine 5'-monophosphate-deoxycytidine 5'-monophosphate-uridine 5'-monophosphate-doexyuridine 5'-monophosphate (CMP-dCMP-UMP-dUMP) kinase, and their molecular weights were calculated to be 46,000 and 26,000, respectively, by gel filtration. dTMP-dUMP kinase phosphorylated dTMP with a Km of 3.1 X 10(-5)M and dUMP with a Km of 7.7 X 10(-4) M. dTMP phosphorylation catalyzed by dTMP-dUMP kinase was inhibited competively by dUMP with a Ki of 2.0 X 10(-3) M. Similarly, phosphorylation of dUMP by this enzyme was inhibited competively by dTMP with a Ki of 2.5 X 10 (-5) M. CMP-dCMP-UMP-dUMP kinase of Yoshida sarcoma phosphorylated dUMP with a Km of 3.1 X 10(-3) M and dCMP with a Km of 7.1 X 10 (-4) M, but it did not phosphorylate dTMP. Phosphorylation of dUMP BY CMP-dCMP-UMP-dUMP kinase was inhibited competitively by DCMP and dTMP with Ki's of 6.9 X 10(-4) and 3.0 X 10(-3) M, respectively, and phosphorylation of dCMP was inhibited completely by dUMP a Ki of 2.2 X 10(-3) M. Relative Vmax activity of this enzyme was 345 nmoles/mg protein with dCMP and 127 nmoles/mg protein with dUMP.

Animals↗
PubMed1977

Role of potassium in the synthesis and decay of two specific bacteriophage T4 messages.

The role of K+ in the in vivo metabolism of specific phage T4 messengers was studied. By using a mutant of Escherichia coli defective in its ability to accumulate K+ from the growth medium, it was possible to rapidly deplete cells of their intracellular K+ and in this way determine K+-dependent reactions in vivo. The rate constants for accumulation, synthesis, and decay of the early enzymes deoxynucleotide kinase and alpha-glucosyl transferase were determined. It was shown that there is a very close association between mRNA synthesis and its decay, indicating that a mechanism may be present in the cell that can regulate the concentration of these RNAs. Since the mRNA's for these enzymes are very stable in cells depleted of K+, K+ depletion may be a useful method for the isolation of functional T4 mRNA.

Coliphages↗
PubMed1976

Activation of rat liver pyrimidine nucleoside monophosphate kinase.

The activity of the pyrimidine nucleoside monophosphate kinase (ATP:dCMP phosphotransferase, EC 2.7.4.14) from rat liver is dependent upon the presence of sulfhydryl-reducing agents. Addition to the inactive enzyme of 2-mercaptoethanol (5 mM), a reagent specific for cleavage of disulfide bonds, effects a reduction in molecular weight from approx. 53 000 to 17 000, measured by molecular sieve chromatography. This low molecular weight form is partially active in the presence of 2-mercaptoethanol (f mM). In absence of 2-mercaptoethanol, the low molecular weight form is inactive. Higher concentrations of 2-mercaptoethanol (50 mM) fully reactivate the CMP(ATP) kinase activity followed by dCMP(ATP) and CMP(dCTP) kinase activities in a sequential manner, without further change in moelcular weight. Alkylation by iodoacetamide of the enzyme at different stages of reactivation in dithiothreitol suggests an ordered appearance of the various enzyme activities. Furthermore, iodoacetamide inactivates the fully active enzyme. Thioredoxin was found to activate the enzyme in a manner similar to 2-mercaptoethanol and dithiothreitol. These results are consistent with the interpretation that the mechanism of activation of the enzyme involves cleavage of inter- and intramolecular disulfide bonds.

Adenosine Triphosphate↗
PubMed1979

Kinetics and equilibria of pyrimidine nucleoside monophosphate kinase from human erythrocytes.

The common type of pyrimidine nucleoside monophosphate kinase (ATP:CMP phosphotransferase, EC 2.7.4.14), purified 50 000-fold from human erythrotes, reacted with a wide variety of nucleotides, but only ATP, dATP, UMP and CMP were good substrates. The optimum Mg2+ concentration, 2-3 mM, was generally independent of substrate concentration, of the nature of the substrate, and of the direction of the reaction. Kinetic studies indicated that a ternary complex was formed, that the substrates were bound at two unlike sites, and that the order of addition of substrates was random. Equilibrium constants were ATP + UMP 0.98, ATP + CMP 1.59, dATP + UMP 1.13, and ATP + AMP 1.20.

Adenosine Triphosphate↗
PubMed1979

Depression of DNA synthesis in mouse spleen after treatment with 5-aza-2'-deoxycytidine.

5-Aza-2'-deoxycytidine is a highly effective cytostatic agent that preferentially affects the lymphatic system. Pretreatment of noninbred H mice with the drug markedly depressed the level of thymidine (dThd) incorporation into DNA in the spleen and also lowered the dThd and thymidylate kinase activities. Maximum effects were observed following administration of the analog in a single dose 24 hours before the mice were killed. Whereas cytidine and dThd did not reverse the inhibitory effect of 5-aza-2'-deoxycytidine, excessive doses of deoxycytidine partially reversed this inhibition. Similar to the depression of dThd incorporation, a depression in the incorporation of deoxycytidine and cytidine into spleen DNA was found after 24-hour pretreatment with 5-aza-2'-deoxycytidine. However, 7 days following 5-aza-2'-deoxycytidine treatment, the incorporation of dThd into DNA in the spleens of mice was significantly increased. [3H]5-aza-2'-deoxycytidine was rapidly incorporated into spleen DNA, whereas deoxycytidine interfered with the incorporation of [3H]5-aza-2'-deoxycytidine.

Animals↗
PubMed1976

Pyrimidine ribonucleoside monophosphokinase and the mode of RNA turnover in Bacillus subtilis.

A protein catalyzing the phosphorylation of CMP to CDP was purified and characterized. Kinase activity for UMP copurified during ammonium sulfate fractionation, DEAE-cellulose and hydroxylapatite chromatography, and gel filtration on Sephadex G-75, the ratios of activities for the two substrates remaining constant. The purified product, possessing both activities was homogeneous as judged by the single band following polyacrylamide gel electrophoresis. The protein showed no kinase activity against purine nucleoside monophosphates or the other pyrimidine nucleoside monophosphates: dCMP, dUMP, and dTMP. Thus unlike the enteric bacteria, Escherichia coli and Salmonella typhimurium which have distinct enzymes which phosphorylate UMP and CMP, Bacillus subtilis produces a single pyrimidine ribonucleoside monophosphokinase. The Km values of this enzyme from B.subtilis are 0.04 and 0.25 mM for CMP and UMP, respectively, and 0.04 and 0.4 mM for ATP at saturating concentrations of CMP and UMP, respectively. The properties of this enzyme and the differences between enteric bacteria and B.subtilis with respect to the enzymes which phosphorylate CMP are consistent with the measurements which indicate that turnover of messenger RNA is largely hydrolytic in E.coli but largely phosphorolytic in B.subtilis.

Bacillus subtilis↗
PubMed1977

Human thymidylate kinase. Purification, characterization, and kinetic behavior of the thymidylate kinase derived from chronic myelocytic leukemia.

Thymidylate kinase derived from the blast cells of human chronic myelocytic leukemia was purified 2186-fold to near homogeneity by means of alcohol precipitation, alumina-Cgamma gel fractionation, calcium phosphate gel fraction, ultrafiltration, and affinity column chromatography. The molecular weight was estimated by glycerol gradient centrifugation to be 50,000. This enzyme had an optimal activity at pH 7.1 and required a divalent cation in order to catalyze the reaction. Mg2+ and Mn2+ were found to be the preferential divalent cations. The activation energy was estimated to be 19.1 kcal/mol at pH 7.2. Initial velocity study suggested that the reaction followed a sequential mechanism. Mg2+ ATP had a Km of 0.25 mM and dTMP had a Km of 40 micrometer. The enzyme was unstable even at 4 degrees. In the presence of ATP or dTMP the enzyme maintained its activity. Purine triphosphate nucleosides were found to be better phosphate donors than the pyrimidine triphosphate nucleosides. ATP and dATP had a lower Km and a higher Vmax than GTP and dGTP. dTMP was the only preferred phosphate receptor among all the monophosphate nucleotides tested dTTP and IdUTP competed with both substrates and inhibited the reaction with a Ki of 0.75 mM and 1.1 mM, respectively.

Chromatography, Affinity↗
PubMed1976

Changes in the activities of nucleoside triphosphatases and nucleoside kinases in Vero cells infected with Simian virus 40.

Changes in the activities of three enzymes involved in nucleotide metabolism were studied following infection of Vero cells with SV40. The results showed that SV40 infection enhanced the activities of uridine phosphokinase and UMP phosphokinase involved in nucleotide synthesis and suppressed the activity of nucleoside triphosphatases involved in nulceotide degradation. These SV40-induced enzyme activity changes probably served to somehow increase the quantity of nucleotides for virus proliferation.

Animals↗