Cloning and characterization of the multisubstrate deoxyribonucleoside kinase of Drosophila melanogaster

A Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) was reported to phosphorylate all four natural deoxyribonucleosides as well as several n ucleoside analogs (Munch-Petersen, B., Piskur, J., and Sondergaard, L. (199 8) J. Biol. Chem. 273, 3926-3931). The broad substrate specificity of this enzyme together with a high catalytic rate makes it unique among the nucleo side kinases, We have in the present study cloned the Dm-dNK cDNA, expresse d the 29-kDa protein in Escherichia colt, and characterized the recombinant enzyme for the phosphorylation of nucleosides and clinically important nuc leoside analogs. The recombinant enzyme preferentially phosphorylated the p yrimidine nucleosides dThd, dCyd, and dUrd, but phosphorylation of the puri ne nucleosides dAdo and dGuo was also efficiently catalyzed. Dm-dNK is clos ely related to human and herpes simplex virus deoxyribonucleoside kinases. The highest level of sequence similarity was noted with human mitochondrial thymidine kinase 2, and these enzymes also share many substrates. The cDNA cloning and characterization of Dm-dNK will be the basis for studies on th e use of this multisubstrate nucleoside kinase as a suicide gene in combine d gene/chemotherapy of cancer.