2.4.2.7 drug development the enzyme is a target for antileishmanicidal drug development 676318 2.4.2.7 medicine expression of both Escherichia coli purine nucleoside phosphorylase and human adenine phosphoribosyl transferase in tumor cell lines. Purine nucleoside phosphorylase cleaves purine nucleoside analogs to generate toxic adenine analogs, which are activated by adenine phosphoribosyl transferase to metabolites that inhibit RNA and protein synthesis. In vivo studies with 6-methylpurine-2'-deoxyriboside, 2-fluoro-2'-deoxyadenosine or 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-phosphate indicate that increased adenine phosphoribosyl transferase in human tumor cells coexpressing Escherichia coli purine nucleoside phosphorylase does not enhance either the activation or the anti-tumor activity of any of the three prodrugs. Expression of excess adenine phosphoribosyl transferase in bystander cells improves the activity of 6-methylpurine-2'-deoxyriboside, but diminishes the activity of 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-phosphate. In vitro studies indicate that increasing the expression of adenine phosphoribosyl in the cells does not significantly increase the activation of 6-methylpurine 721965 2.4.2.7 synthesis purine nucleotide synthesis using TthAPRT and TthHPRT (EC 2.4.2.8) 758715