Cobamides and Ribonucleotide Reduction. IV. Stereochemistry of Hydrogen Transfer to the Deoxyribonucleotide^*

Pyrimidine metabolism in microorganisms.

“…The stereochemistry of the reduction of ribonucleoside triphosphates catalyzed by the reductase of L. leichmannii has been studied by techniques similar to those used for the E. coli enzyme. The results were identical, indicating that also the coenzyme Bu2-dependent ribonucleotide reductase from L. leichmannii catalyzes a stereospecific replacement of the 2'-OH group of the substrates with hydrogen (28,52,137,155,161). In the presence of reduced lipoic acid and a ribonucleoside triphosphate, the ribonucleoside triphosphate reductase catalyzed the transfer of tritium from 8H20 (in equilibrium with the hydrogens of the thiol groups of reduced lipoic acid) to the 5'position of the coenzyme and into the 2'-position of the deoxyribonucleoside triphosphate product, suggesting that coenzyme B12 functions as a hydrogen carrier during the reaction (6,185).…”

Mechanism of Inhibition of Deoxyribonucleic Acid Synthesis in Escherichia coli by Hydroxyurea

“…These results strongly suggest that exposure of cells to HU for up to 0.5 hr has little or no effect DNA synthesis in toluene-treated cells. 4…”

“…One culture also contained 0.5 ,sCi of '4C-thymidine per ml, and the second contained 25 MCi of 3H-thymidine per ml. When the cell density reached about 4 x 101 cells/ml, 2-ml samples were withdrawn, filtered on membrane filters (Millipore Corp.), washed with 10 ml of cold M9CA medium, and resuspended in 2 ml of prewarmed M9CA medium. The "4C-labeled cells were added to a medium that also contained 26 mm HU.…”

Biochemical functions of corrinoid compounds. The sixth Hopkins memorial lecture

“…Gottesman & Beck (1966) and Blakley, Ghambeer, Batterham & Brownson (1966) found that solvent hydrogen is added exclusively to C-2', as it is also in the E. coli ribonucleotide reductase system (Larsson, 1965). Further, Batterham, Ghambeer, Blakley & Brownson (1967) concluded by examining the protonmagnetic-resonance spectrum of 2H-labelled deoxyadenosine derived from deoxy-ATP, which had been prepared by enzymic reduction of ATP in 2Hlabelled water solution, that the 2H is added to C-2' with retention of configuration. It has been suggested that the reaction involves a displacement of an OHion by an H-ion.…”