Molecular Pharmacology, Vol 7, 413-419, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

Studies on the Phosphorylation of Cytosine Arabinoside in Mammalian Cells

¹ McGill University Cancer Research Unit, Montreal, Quebec, Canada

The effect of cytosine arabinoside 5'-triphosphate (araCTP) on the phosphorylation of deoxycytidine or cytosine arabinoside by deoxycytidine kinase and the phosphorylation of deoxyadenosine by deoxyadenosine kinase has been studied. AraCTP was a potent inhibitor of the phosphorylation of cytosine arabinoside and deoxyadenosine, but not of deoxycytidine. The inhibition produced by araCTP appeared to be competitive with respect to the phosphate donor, ATP, for both deoxycytidine kinase and deoxyadenosine kinase.

The phosphorylation of cytosine arabinoside was measured in sonic extracts of HeLa cells obtained from different phases of the cell cycle. The rate of phosphorylation of cytosine arabinoside appeared to increase significantly during the S phase of the cell cycle.