The effect of culture conditions on the glutamylation of methotrexate by intact H35 hepatoma cells and folylpolyglutamate synthetase (FPGS) activity in the corresponding crude extracts has been examined. The rate of cellular glutamylation of methotrexate observed in rapidly dividing cultures was 4-fold higher than confluent cultures, and was accompanied by an increase in extract FPGS activity (...

INTRODUCTION 5-Fluorouracil and methotrexate are antimetabolites widely used in the treatment of neoplastic disease. They act by inactivating the two enzymes involved in the biosynthesis of the pyrimidine nucleotide 2’-deoxythymidine 5’-monophosphate, namely thymidylate synthase and dihydrofolate reductase. The three dimensional structure of each enzyme is known and the mechanisms of the reacti...

Is the enzymatic machinery for DNA precursor biosynthesis linked to the DNA replication apparatus? To identify intermolecular associations among deoxyribonucleotide biosynthetic enzymes and to ask whether these enzymes are linked to replication proteins, we analyzed radiolabeled T4 bacteriophage proteins that bind specifically to a column of immobilized T4 deoxycytidylate hydroxymethylase. More...

In humans, the gene encoding a reverse thymidylate synthase (rTS) is transcribed in the reverse direction of the gene encoding thymidylate synthase (TS) that is involved in DNA biosynthesis. Three isoforms are found: α, β, and γ, with the transcript of the α-isoform overlapping with that of TS. rTSβ has been of interest since the discovery of its overexpression in methotrexate and 5-fluorouraci...

Protein in vitro inhibition of thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45) by 5-fluoro-2'-deoxyuridylate requires 5,10-methylenetetrahydrofolate. The cytoxicity of 5-fluoro-2'-deoxyuridine towards cultured L1210 mouse leukemia cells is reduced when intracellular reduced folates are depleted, either by limiting the source in media or by inhibition ...

Tomudex (ZD1694) is a quinazoline-based folate analog and a powerful inhibitor of cellular thymidylate synthase and is approved in Europe for use in oncology. Here the first evidence of its activity against murine and human cytomegalovirus (MCMV and HCMV) is reported. ZD1694 irreversibly inhibited the replication and DNA synthesis of both viruses in quiescent fibroblasts. The corresponding 50% ...