Murakami K, Tsushima K
Biochim Biophys Acta. 1975 Apr 19;384(2):390-8. doi: 10.1016/0005-2744(75)90040-6.
Purine nucleoside phosphorylase (purine nucleoside:orthophosphate ribosyltransferase, EC 2.4.2.1) from chicken liver has been purified about 650 fold and crystallized. The crystalline enzyme was cube shaped and showed a specific activity of 46 units per mg of protein. The homogeneity of the crystalline enzyme was shown by polyacrylamide gel-disc electrophoresis. The sedimentation coefficient (s-degrees 2o,w) was 5.4 S. The crystalline enzyme was activated by the substrate inosine. The Hill coefficient was estimated to be 0.76, suggesting negative cooperativity with regard to the substrate inosine. The results of the kinetic analysis are consistent with the mechanism being a "rapid equilibrium random Bi-Bi reaction". The apparent equilibrium constant for phosphorolysis was 0.048.
鸡肝中的嘌呤核苷磷酸化酶（嘌呤核苷：正磷酸核糖基转移酶，EC 2.4.2.1）已被纯化约650倍并结晶。结晶酶呈立方体形状，每毫克蛋白质的比活性为46单位。聚丙烯酰胺凝胶圆盘电泳显示结晶酶具有均一性。沉降系数（s20,w）为5.4 S。结晶酶被底物肌苷激活。希尔系数估计为0.76，表明对底物肌苷存在负协同性。动力学分析结果与该机制为“快速平衡随机双底物双产物反应”一致。磷酸解的表观平衡常数为0.048。
