The mechanism of the anaerobic escherichia coli ribonucleotide reductase investigated with nuclear magnetic resonance spectroscopy

During the reduction of ribonucleotides with [³H]formate by the class III anaerobic ribonucleotide reductase from Escherichia coli tritium appears in water and not in the product deoxyribonucleotide. In D₂O, deuterium replaces the OH-group at carbon-2′ with retention of configuration. In addition we find 1-2 % deuterium in the 3′-position demonstrating a small exchange of this hydrogen with the protons of water during catalysis. Class I and II enzymes catalyze identical reactions. Members of the three classes of reductases apparently use the same chemical mechanism in spite of having completely different protein structures.