On the mechanism of ribonucleoside triphosphate reductase from Lactobacillus leichmannii. Evidence for 3' C--H bond cleavage.

The 3' carbon-hydrogen bond of [3'-3H]uridine 5'-triphosphate is is cleaved during its conversion to 2'-deoxyuridine 5'-triphosphate catalyzed by Lactobacillus leichmannii ribonucleoside triphosphate reductase. A selection against 3H of approximately 1.8 is observed on this reduction. During the course of this reaction, no 3H is released to the solvent, and no 3H is recovered in reisolated coenzyme B12. Incubation of [3'-2H]uridine 5'-triphosphate with enzyme resulted in production of 2'-deoxy[3'-2H]uridine 5'-triphosphate.