Cytidylate-deoxycytidylate kinase

Thus, while existence of a cytidylate-deoxycytidylate kinase is established, there remains some uncertainty about the association of uridylate kinase activity with this enzyme. Phosphorylation of deoxyuridylate appears to be catalyzed by a separate enzyme activity, possibly by thymidylate kinase. 

As a further instance of a dual function for the nucleoside monophosphate kinases, separate kinases for adenylate-deoxyadenylate, guanylate-deoxyguanylate, cytidylate-deoxycytidylate, uridylate, and thynudylate have been demonstrated in E. cdi extracts (35) it should be noted that cytidylate-deoxycytidylate kinase and uridylate kinase were found as separate enzyme activities in the E. cdi experiments. 

Sugino el al. 17) have partly purified a deoxycytidylate kinase from calf thymus this preparation also phosphorylates cytidylate and uridylate, but not deoxyuridylate. The deoxyuridylate kinase activity was recovered in another protein fraction and so represents a distinct entity. As phosphate donors, only ATP and dATP were active in the cytidylate reaction. 

Fractionation of extracts from calf thymus for kinase activity toward deoxyribonucleoside monophosphates has revealed the presence of at least four separate enzymes the kinase activities for dAMP, dGMP, dCMP, and dTMP are separate entities in this tissue 31). Each has been partly purified and examination of substrate specificities showed that the kinases for deoxyadenylate and deoxyguanylate also phosphorylate the ribosyl homologues, adenylate and guanylate, respectively. The deoxycytidylate kinase accepts as substrates both cytidylate and uridylate, but will not phosphor> late deoxyuridylate. The calf thymus thymidine monophosphate... 

---