Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of polyamines on the various activities of DNA polymerase I from Escherichia coli (EC 2.7.7.7) has been investigated. For all high molecular weight DNAs spermine and spermidine caused up to 80% inhibition when present in high concentrations, i.e. above 1 mM for spermine and 2 mM for spermidine. In the presence of low concentrations of polyamines a small activation was seen for some DNAs. The diamines cadaverine and putrescine had little influence on the rate of synthesis with natural occurring DNAs. In the case of d(A--T)n the activation/inhibition was found to be markedly dependent on the molecular weight of the samples used. With a low molecular weight DNA, 5.6 S, addition of spermidine resulted in up to 3-fold stimulation of activity. The activation was dependent on the concentration of MgCl2 and ionic strength; increasing concentration of these gave a decrease in the degree of activation. Polyamines also had a dramatic effect on the rate of synthesis using the homopolymers (dA)n . (dT)10 and (rA)n . (dT)10 . (20:1) as primers. Putrescine, in particular, increased the activity up to 10-fold with (rA)n . (dT)10 and somewhat less for (dA)n . (dT)10. The apparent Km for the primer (rA)n . (dT)10 decreased approx. 35-fold in the presence of 6.6 mM putrescine. There was no influence on the apparent Km for dTTP. The influence of polyamines on both the 5' leads to 3' and 3' leads to 5' nuclease activity was also investigated. Inhibition of nuclease activity was observed in the presence of polyamines, particularly with spermine. Thus with d(A--T)n and T7 DNA as substrates addition of 0.7 mM spermine resulted in almost complete inhibition of the activity. The dramatic inhibition observed with high concentrations of spermine (spermidine) both in the case of polymerizing and nuclease activity is thought to be due to polyamine-induced aggregation of DNA molecules.
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PMID:Influence of polyamines on the activity of DNA polymerase I from Escherichia coli. 36 Oct 88

DNA polymerase from the malarial parasite Plasmodium falciparum required Mg2+ for activity, Putrescine (1 mM) caused a twofold increase in enzyme activity in the presence of a suboptimal concentration of MgCl2 (2 mM). Spermidine (1.5-2.0 mM) or spermine (0.1-0.3 mM) increased the activity of malarial DNA polymerase, in the presence of 2 mM MgCl2, by factors of 6 and 3-5, respectively. The activity of DNA polymerase from calf thymus or from NIH 3T3 cells transformed by the ras oncogene were not stimulated by these polyamines to the same extent. These findings suggest that in malaria-infected erythrocytes, polyamines, at physiological concentrations, serve as a cofactor for the parasitic alpha-like DNA polymerase. Malarial parasites grown in cultured human erythrocytes did not synthesize DNA after treatment with alpha-difluoromethylornithine, which caused polyamine depletion in the infected cells. DNA synthesis was resumed after adding putrescine to the polyamine-depleted cultures. DNA synthesis was also initiated when actinomycin D was added along with putrescine to polyamine-depleted cells. It thus appears that polyamines are essential for the translation of the DNA polymerase mRNA and that polyamines play an important role in regulating the cell cycle of the malarial parasite.
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PMID:Effect of polyamines on the activity of malarial alpha-like DNA polymerase. 220 98

The role of polyamine in the proliferation of cultured mouse L cells was investigated using DL-alpha-hydrazino-delta-aminovaleric acid (DL-HAVA), a potent and competitive inhibitor of ornithine decarboxylase [EC 4.1.1.17]. When confluent mouse L cells were reseeded, the intracellular concentration of polyamines increased sharply, and the maximal levels of putrescine, spermidine, and spermine were 3.3, 2.2, and 1.8 times their initial values, respectively, one or two days after inoculation. DL-HAVA produced prompt depletion of the intracellular putrescine and spermidine contents and a further increase of the spermine level to 30-90% more than that of the control throughout the experiment. The total level of the three polyamines was reduced to a great extent in DL-HAVA-treated cells. Concomitant with the disappearance of the two polyamines, cell proliferation, measured as the total cell number and DNA accumulation, was greatly suppressed by the inhibitor. Addition of exogenous putrescine or spermidine with or after DL-HAVA restored the inhibited cell growth in a dose-dependent manner. Putrescine administered to inhibitor-treated cultures was rapidly incorporated into the cells and effectively converted to spermidine. Addition of spermidine to the culture medium also normalized the intracellular spermidine content, but the putrescine level remained unchanged. Neither cadaverine nor 1,3-diaminopropane, structural analogs of putrescine, overcame the inhibition under the same conditions. Thymidine kinase [EC 2.7.1.21] activity and the pools of triphosphates of thymidine and deoxyadenosine were appreciably reduced in DL-HAVA-treated cells, whereas DNA polymerase [EC 2.7.7.7] activity was not changed significantly. These findings suggest that spermidine might play essential roles in the metabolism of deoxyribonucleoside triphosphates and growth of mouse L cells in culture.
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PMID:Inhibition of polyamine synthesis and proliferation in mouse L cells by DL-alpha-hydrazino-delta-aminovaleric acid, an inhibitor of ornithine decarboxylase. 661 23

Putrescine biosynthesis is elevated before DNA replication, and a stimulation of DNA synthesis by 20 mM putrescine has been found using an in vitro DNA synthesizing system. Furthermore, this stimulation of DNA synthesis by putrescine involves a particular factor (factor PA). This factor PA stimulates DNA polymerases alpha, beta, and gamma, and is present in nuclei and mitochondria but not in cytoplasm. Factor PA loses about 80% of its activity by heating at 45 degrees C for 15 min or by hydrolysis with 100 mg ml(-1) Enzygel trypsin. These properties indicate that factor PA is a protein. Its size is estimated to be about 2.1 S. DNA synthesis in nuclear and mitochondrial DNA polymerase extracts from tumour tissues and host livers of tumour-bearing rats are not stimulated by 20 mM putrescine. However, the addition of excess factor PA to DNA synthesizing systems using DNA polymerase extracts from proliferative tissues again results in a stimulation of DNA synthesis by exogenous putrescine. These findings indicate that the stimulatory effect of DNA synthesis in vitro by exogenous putrescine is controlled by the ratio between factor PA and endogenously synthesized putrescine in proliferative tissues or that sent by the bloodstream from proliferative tissues. These results suggest that a non-stimulatory effect of putrescine on DNA synthesis may be diagnostic in tumour-bearing patients.
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PMID:The difference in the stimulation by putrescine of DNA synthesis using DNA polymerase extracts of normal rat liver or of tumour tissue or host liver from tumour-bearing rats. 1212 97