Stinson R A, McPhee J L, Collier H B
Biochim Biophys Acta. 1987 Jul 7;913(3):272-8. doi: 10.1016/0167-4838(87)90135-x.
Purified isoenzymes of human alkaline phosphatase from placenta, intestine and liver were investigated as catalysts for phosphotransferase activity, using the phosphoacceptors Tris, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, diethanolamine, 2-(ethylamino)ethanol, ethanolamine, and N-methyl-D-glucamine. All of the compounds supported phosphotransferase catalysis, conforming to saturation kinetics. There was little difference among the isoenzymes with respect to Km values of the acceptors, but the liver form was the most efficient (highest Vmax/Km) in forming phosphoacceptors; it was also the most efficient (highest Vamax/Ka) when the phosphoacceptors were considered as activators. At Vmax the isoenzymes differed little in their support of phosphotransferase activity relative to phosphohydrolysis, although the intestinal enzyme tended to be the poorest. The two best acceptors were diethanolamine, providing the highest phosphotransferase velocity, and 2-(ethylamino)ethanol, having the lowest Km. The phosphoaceptors that bound Zn2+ tightly did not function well in the phosphotransferase reaction, and vice versa. However, temporal assessment of the phosphohydrolytic and phosphotransferase activities during removal of Zn2+ from the enzyme with 1,10-phenanthroline revealed no evidence of a special role for Zn2+ in the latter activity.
对从胎盘、肠道和肝脏中纯化得到的人碱性磷酸酶同工酶进行了研究，以磷酸受体Tris、2-氨基-2-甲基-1-丙醇、2-氨基-2-甲基-1,3-丙二醇、二乙醇胺、2-(乙氨基)乙醇、乙醇胺和N-甲基-D-葡糖胺作为磷酸转移酶活性的催化剂。所有这些化合物均支持磷酸转移酶催化，符合饱和动力学。这些同工酶在受体的Km值方面差异不大，但肝脏型在形成磷酸受体方面效率最高（Vmax/Km最高）；当将磷酸受体视为激活剂时，它也是效率最高的（Vamax/Ka最高）。在Vmax时，尽管肠道酶往往是最差的，但同工酶在支持磷酸转移酶活性相对于磷酸水解方面差异不大。两个最佳受体是二乙醇胺，其提供最高的磷酸转移酶速度，以及2-(乙氨基)乙醇，其Km最低。紧密结合Zn2+的磷酸受体在磷酸转移酶反应中不起作用，反之亦然。然而，在用1,10-菲咯啉从酶中去除Zn2+的过程中对磷酸水解和磷酸转移酶活性进行的时间评估显示，没有证据表明Zn2+在后者的活性中起特殊作用。
