THE MECHANISM OF THE ANAEROBIC ESCHERICHIA-COLI RIBONUCLEOTIDE REDUCTASE INVESTIGATED WITH NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

During the reduction of ribonucleotides with [H-3]formate by the class III anaerobic ribonucleotide reductase from Escherichia coli tritium appears in water and not in the product deoxyribonucleotide. In D2O, d euterium replaces the OH-group at carbon-2' with retention of configur ation. In addition we find 1-2 % deuterium in the 3'-position demonstr ating a small exchange of this hydrogen with the protons of wa ter dur ing catalysis. Class I and II enzymes catalyze identical reactions. Me mbers of the three classes of reductases apparently use the same chemi cal mechanism in spite of having completely different protein structur es. (C) 1995 Academic Press. Inc.