Purine nucleoside phosphorylase of chicken liver

Abstract Purine nucleoside phosphorylase (purine nucleoside:orthophosphate ribosyltransferase, EC 2.4.2.1) has been purified 125-fold from the homogenate of chicken livers and some of the properties of the purified enzyme have been studied. This enzyme had a pH optimum at around 6.o. At high substrate levels of inosine the reaction rate was increased, suggesting that substrate activation of the enzyme had occurred. The enzyme activity was completely lost after 48 h at −20°. The inhibition by nucleotides and SO 4 2− is a characteristic of this enzyme and has not been previously reported.