Induction of thymidine kinase and DNase in varicella-zoster virus-infected cells and kinetic properties of the virus-induced thymidine kinase

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Abstract
Thymidine kinase (TK), DNA polymerase, and DNase activities were induced in human foreskin fibroblasts after varicella-zoster virus infection. The induced TK and DNase activities had electrophoretic mobilities different from the corresponding host enzymes. Varicella-zoster virus-induced TK was purified and separated from the host enzyme by affinity column chromatography. This enzyme had a broader substrate specificity with respect to either the phosphate donor or acceptor as compared with human cytoplasmic and mitochondrial TK. The best phosphate donor was ATP, with a Km of 16 .mu.M. The Km values of thymidine, deoxycytidine, and 5-propyl deoxyuridine were estimated to be 0.4, 180 and 0.8 .mu.M, respectively. The Ki [inhibition constant] values for several analogs of thymidine such as 5-iododeoxyuridine, arabinofuranosylthymine, 5-ethyl deoxyuridine and 5-cyanodeoxyuridine were also examined. TTP acted as a noncompetitive inhibitor with respect to thymidine with a Ki of 5 .mu.M. The kinetic behavior of varicella-zoster virus-induced TK is different from human cytoplasmic, human mitochondrial and herpes simplex virus types 1- and 2-induced TK.

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