The effect of nitrous oxide on intracellular folate metabolism of the human bone marrow was studied in vitro. Bone marrow cells, obtained from healthy volunteers, were incubated with 5 x 10(-8)m-[(3)H]5-formyltetrahydrofolate (5-formylTHF) for 18 hr to label intracellular folate pools. Subsequently the cells were exposed to nitrous oxide for up to 10 hr, and the intracellular folate coenzyme le...

Gene 1.7 of bacteriophage T7 confers sensitivity of both phage T7 and its host Escherichia coli to dideoxythymidine (ddT). We have purified the product of gene 1.7, gp1.7. It exists in two forms of molecular weight 22,181 and 17,782. Only the C-terminal half of the protein is required to confer ddT sensitivity. We show that gp1.7 catalyses the phosphorylation of dGMP and dTMP to dGDP and dTDP, ...

The occurrence of a dTMP kinase as well as a dTDP kinase in Acetabularia mediterranea has been demonstrated. A test system was developed by which it was possible to estimate the enzyme activity in an individual Acetabularia cell or even in a cell fragment. The enzyme catalyses the phosphorylation of dTMP in the presence of ATP. In the test system described, dTTP is formed as well as dTDP. This ...

Numerous investigations have focused on DNA damage induced by ionizing radiation; however, photoionization threshold energies of nucleic acid components in aqueous solution are not known. Herein, data from gas-phase photoelectron experiments have been combined with results from self-consistent field and post-self-consistent field molecular orbital calculations and with theoretical Gibbs free en...

The kinetics of the reaction catalyzed by thymidylate synthase from Lactobacillus casei were investigated at pH 6.8 and 30” with the natural isomer of 5,10-methylene5,6,7&tetrahydrofolate ((+)-CH,-H,folate). An apparatus for adding the enzyme to the reaction mixture and rapidly mixing without opening the sample compartment allowed the acquisition of spectrophotometric rate data within a few sec...

The de novo and salvage dTTP pathways are essential for maintaining cellular dTTP pools to ensure the faithful replication of both mitochondrial and nuclear DNA. Disregulation of dTTP pools results in mitochondrial dysfunction and nuclear genome instability due to an increase in uracil misincorporation. In this study, we identified a de novo dTMP synthesis pathway in mammalian mitochondria. Mit...

The kinetics of the reaction catalyzed by thymidylate synthase from Lactobacillus casei were investigated at pH 6.8 and 30” with the natural isomer of 5,10-methylene5,6,7&tetrahydrofolate ((+)-CH,-H,folate). An apparatus for adding the enzyme to the reaction mixture and rapidly mixing without opening the sample compartment allowed the acquisition of spectrophotometric rate data within a few sec...

The deoxythymidylate phosphohydrolase (dTMPase) induced by Bacillus subtilis bacteriophage PBS2 (whose DNA contains uracil instead of thymine) has been partially purified and shown to possess deoxyuridylate phosphohydrolase (dUMPase) activity. The similarities of induction period, pH dependence, heat and trypsin inactivation, sulfhydryl reagent and fluoride inhibition, metal ion effects, kineti...

An improved method for isolation of yeast m utants auxotrophic for 5'-dTM P is presented. The procedure employs the two folic acid antagonists aminopterin and sulfanilamide (SA A). Selec­ tiveness of the procedure depends on concentration of SAA and time of incubation. 44 mutants auxotrophic and 3 conditionally auxotrophic for 5'-dTMP were isolated. All belong to one complementation group. The ...