[Purine nucleoside phosphorylase. Catalytic reaction mechanism. II. Product-reaction-inhibition (author's transl)].

According to Cleland's theoretical predictions, inosine phosphorolysis catalyzed by chicken and pigeon's liver PNPase (Purine nucleoside:ortophosphate ribosyltransferase. E.C. 2.4.2.1.) appears to be a rapid equilibrium random bi-bi with "dead end" enzyme-phosphate-hypoxantine complex. This mechanism implies the existence of two essential active centers in the enzymatic molecule to which inosine and phosphate attach themselves independently. The observed lack of analogy in the PNPase mechanism of mechanism of different species seems to suggest the existence of structural differences between them.