Mutant herpes simplex virus type 1 thymidine kinase SR39 (HSV-1 TK SR39)

Mutant herpes simplex virus type 1 thymidine kinase SR39 is a genetically engineered variant of the HSV-1 thymidine kinase enzyme, created via random mutagenesis to enhance its ability to phosphorylate nucleoside analog prodrugs, particularly ganciclovir and acyclovir. This kinase is a crucial component of suicide gene therapy whereby tumor cells expressing the SR39 variant become highly sensitive to prodrugs that are otherwise non-toxic. Once these prodrugs are introduced, SR39 efficiently phosphorylates them to toxic metabolites that are incorporated into DNA, resulting in selective tumor cell death. SR39 possesses multiple amino acid substitutions in its active site, which confer a significantly decreased *K*~m~ and improved catalytic efficiency for prodrug substrates compared to the wild-type enzyme, making it more effective for gene therapy applications[1][2][4].

Other names

HSV thymidine kinase SR39HSV1-tk SR39HSV TK SR39SR39 mutant thymidine kinase

Prodrug activation: Phosphorylation of nucleoside analog prodrugs (especially ganciclovir and acyclovir), leading to formation of toxic nucleoside triphosphates that inhibit DNA synthesis and trigger cell death[1][2][4].