It was observed that 10% of urine culture isolates of enterococci tested for antimicrobial susceptibility failed to grow on commercially prepared Mueller-Hinton agar with low levels of thymidine and thymine. All strains could utilize exogenous thymidine and thymine and required only low levels (0.4-microgram disk) to support growth. All thymidine-thymine-requiring strains were resistant to trim...

By chromatography on diethylaminoethyl Sephadex, three enzyme fractions with pyrimidine nucleoside phosphorylase activity have been separated from extracts of normal or regenerating liver of rats. Two of these probably represent isoenzymes of uridine phosphorylase. Both are phosphate-dependent and both exhibit maximal activities toward uridine, deoxyuridine, and thymidine at pH values of 7.9 to...

Thymidine derivatives of this type are uncommon and only recently have thymidine diphosphate rhamnose I and related deoxysugar nucleotides 17 been described. Guanosine diphosphate mannosO 8 is the only other nucleotide containing mannose. Thymidine diphosphate mannose is of interest as a possible intermediate in the biosynthesis of streptomycin B (a-D-mannopyranosyl-streptomycin) TM, which occu...

Positron emission tomography can be used to image tumor proliferation when combined with appropriate labeled tracers, such as the thymidine analog [(18)F]-3'-deoxy-3'-fluorothymidine. Although thymidine kinase 1 is the principal mechanism of cell trapping, other variables, such as the cellular level of native thymidine, may need to be considered.

By chromatography on diethylaminoethyl Sephadex, three enzyme fractions with pyrimidine nucleoside phosphorylase activity have been separated from extracts of normal or regenerating liver of rats. Two of these probably represent isoenzymes of uridine phosphorylase. Both are phosphate-dependent and both exhibit maximal activities toward uridine, deoxyuridine, and thymidine at pH values of 7.9 to...

We quantify cytosolic and mitochondrial deoxyribonucleoside triphosphates (dNTPs) from four established cell lines using a recently described method for the separation of cytosolic and mitochondrial (mt) dNTPs from as little as 10 million cells in culture (Pontarin, G., Gallinaro, L., Ferraro, P., Reichard, P., and Bianchi, V. (2003) Proc. Natl. Acad. Sci. U. S. A. 100, 12159-12164). In cycling...

Cytosolic thymidine kinase (EC 2.7.1.21) has been purified 5200-fold to apparent homogeneity from normal human placenta. The purification includes sequential affinity chromatography on blue-Sepharose and a thymidine column. The molecular weight of the enzyme determined by gel filtration and sucrose density ultracentrifugation is 92,000. The subunit molecular weight is 44,000, suggesting that th...

The inhibitory activity of liver extracts on thymidine incorporation into DNA was markedly enhanced by manganese and zinc. Manganese-activated liver extract (Mn-liver extract) also inhibited incorporation of deoxycytidine and adenine into DNA. The Mn-liver extract had no effect on incorporation of thymidine-5'-triphosphate into DNA but blocked the phosphorylation of deoxythymidine. The phosphor...