Ribonucleotide reductase of rabbit bone marrow.

Ribonucleotide reductase activity was increased in extracts of bone marrow from rabbits treated with methyl phenyldiazenecarboxylate, a hemolytic agent which results in an increased number of reticulocytes in blood. The enzyme has been partially purified from bone marrow of rabbits treated with this agent. Enzymatic reduction of cytosine ribonucleotides requires a dithiol, magnesium ions, and ATP and is stimulated by ferrous ions. CDP is a better substrate than CTP or CMP. The purified extracts can be separated into two protein fractions which must be combined for activity, indicating that the enzyme system consists of more than one component.