Purine nucleoside phosphorylase from bovine liver

Abstract 1. 1. Purine nucleoside phosphorylase (purine nucleoside:orthophosphate ribosyltransferase, E.C. 2.4.2.1) from liver of cattle, Bos taurus , was purified to homogeneity. Some properties of the enzymes from three different bovine tissues were compared and discussed. 2. 2. The enzyme has a molecular weight of 83,000, a sedimentation coefficient of 5.3 S. a Stokes' radius of 3.71 nm, a frictional ratio of 1.30 and a subunit molecular weight of 30,000. 3. 3. Optimal pH for xanthosine degradation is around 5.5. whereas a broad pH activity profile for inosine degradation was observed between 5.0 and 7.5. Lineweaver Burk plots curved downward at high concentrations of substrates, inosine, phosphate and arsenate.