PHOSPHORYLATION OF THE ENANTIOMERS OF THE CARBOCYCLIC ANALOG OF 2'-DEOXYGUANOSINE IN CELLS INFECTED WITH HERPES-SIMPLEX VIRUS TYPE-1 AND INUNINFECTED CELLS - LACK OF ENANTIOMERIC SELECTIVITY WITH THE VIRAL THYMIDINE KINASE

CdG, the carbocyclic analog of 2'-deoxyguanosine, is active against he rpes, hepatitis B, and human cytomegaloviruses. We have studied the in teraction of the tritiated enantiomers of CdG with the herpes simplex virus type 1-specific thymidine kinase (HSV-1 TK) and have examined th eir metabolism in uninfected and HSV-1-infected cells. D- and L-CdG we re equally effective competitive inhibitors of the phosphorylation of thymidine (dThd) by the partially purified HSV-1 TK (K(i) values were 2.1 and 3.4 muM, respectively) and were also equal as substrates (K(m) values were 17 and 26 muM, respectively, and V(max) values of the ena ntiomers were equal and about 50% greater than the V(max) for dThd). T he partially purified enzyme preparation, which contained cellular nuc leotide kinase activities (pyruvate kinase also was present in the ass ay medium), converted D-CdG almost exclusively to the triphosphate and L-CdG almost exclusively to the monophosphate. Similarly, in virus-in fected cells the D-enantiomer was converted predominantly to the triph osphate and the L-enantiomer predominantly to the monophosphate. In un infected cells the results were qualitatively similar. In CEM cells de oxycytidine (dCyd) kinase (EC 2.7.1.74) seemed to be the enzyme princi pally responsible for the phosphorylation of both enantiomers, as show n by competition studies. Thus, both the HSV-1 TK and cellular dCyd ki nase (of CEM cells) showed no selectivity for the enantiomers of CdG. This lack of enantiomeric specificity has obvious implications for the design of inhibitors of both viral proliferation and cellular metabol ism.