Metabolism of Deoxyribonucleotides: I. PURIFICATION AND PROPERTIES OF DEOXYCYTIDINE MONOPHOSPHOKINASE OF CALF THYMUS

Abstract

Abstract A procedure for the partial fractionation and purification of dAMP, dGMP, dCMP, and dTMP kinases from calf thymus is described. The results obtained indicate that there are at least four distinct nucleoside monophosphokinases, specific for adenine, guanine, cytosine and uracil, and thymine. The kinase specific toward dCMP was further purified and it was shown that the stability of this enzyme was absolutely dependent on the presence of thiol. The purified dCMP kinase preparation also catalyzed the phosphorylation of CMP and UMP. These three pyrimidine nucleotides were found to be competitive inhibitors for each other. However, under appropriate conditions in the absence of thiol, dCMP kinase activity was lost without appreciable change in the other two kinase activities. The dCMP kinase activity that had been lost was easily restored by incubating with thiol compounds. Several other properties of the purified enzyme are also described.