70] Purine nucleoside phosphorylase from Salmonella typhimurium and rat liver

Abstract

Publisher Summary This chapter describes the purification procedure of purine nucleoside phosphorylase enzyme from Salmonella typhimurium and rat liver. When Salmonella typhimurium is grown in the presence of a purine ribonucleoside, purine nucleoside phosphorylase and phosphodeoxyribomutase are coordinately induced. But when cells are grown in the presence of deoxyribose or deoxyribonucleosides, four enzymes are induced. These include thymidine phosphorylase, purine nucleoside phosphorylase, phosphodeoxyribomutase, and deoxyribose-5-phosphate aldolase. The demonstration that purified purine nucleoside phosphorylase has specificity for both purine ribo- and deoxyribonucleosides is consistent with the hypothesis that a single gene codes for the enzyme but that the gene is regulated by more than one effector. The phosphorylase is present in a relatively high concentration in rat liver tissue accounting for about 0.2% of the soluble protein. The breakdown of inosine is followed by an increase in absorbance at 293 nm produced by uric acid in a coupled assay system with xanthine oxidase.