The multisubstrate deoxyribonucleoside kinase ofDroso-phila melanogaster (Dm-dNK) is sequence-related to three human deoxyribonucleoside kinases and to herpes simplex virus type-1 thymidine kinase. Dm-dNK phos-phorylates both purine and pyrimidine deoxyribonucleo-sides and nucleoside analogues although it has a preference for pyrimidine nucleosides. We performed site-directed mutagenesis on residues that, based on structural data, are involved in substrate recognition. The aim was to increase the phosphorylation efficiency of purine nucleoside sub-stratestocreateanimprovedenzymetobeusedinsuicide gene therapy. .
