Kameyama Y, Yoshioka S, Imai A, Nozawa Y
Biochim Biophys Acta. 1983 Jul 12;752(2):244-50.
Microsomes isolated from human platelets synthesize phosphatidylinositol by the action of acyl-CoA: 1-acyl-sn-glycerol-3-phosphorylinositol(1-acyl-GPI) acyltransferase. The properties of 1-acyl-GPI acyltransferase were compared with those of 1-acyl-glycerophosphorylcholine (1-acyl-GPC) acyltransferase. Apparent Km values of 1-acyl-GPI and 1-acyl-GPC acyltransferases for the corresponding acyl acceptor (lysophospholipid) were 22 and 20 microM, respectively, in the presence of arachidonoyl-CoA as fatty acyl donor. However, the Km value (1.3 microM) of 1-acyl-GPI acyltransferase for arachidonoyl-CoA was much lower than that (5.0 microM) of 1-acyl-GPC acyltransferase. Under optimal conditions, the acylation rate of 1-acyl-GPI with arachidonoyl-CoA was 2-6 times higher than with oleoyl-CoA and linoleoyl-CoA, and was very low with saturated fatty acyl-CoAs. The acylation rates with various acyl-CoAs for 1-acyl-GPI were different from those for 1-acyl-GPC. These results suggest that the reacylation pathway of 1-acyl-GPI participates in the incorporation of arachidonic acid to phosphatidylinositol in platelet microsomes. Furthermore, there were no significant effects of thrombin-activation on acyl-CoA specificity for 1-acyl-GPI and 1-acyl-GPC acyltransferase in human platelets.
从人血小板中分离出的微粒体通过酰基辅酶A：1-酰基-sn-甘油-3-磷酸肌醇（1-酰基-GPI）酰基转移酶的作用合成磷脂酰肌醇。将1-酰基-GPI酰基转移酶的特性与1-酰基甘油磷酸胆碱（1-酰基-GPC）酰基转移酶的特性进行了比较。在花生四烯酰辅酶A作为脂肪酰供体存在的情况下，1-酰基-GPI和1-酰基-GPC酰基转移酶对相应酰基受体（溶血磷脂）的表观Km值分别为22和20微摩尔。然而，1-酰基-GPI酰基转移酶对花生四烯酰辅酶A的Km值（1.3微摩尔）远低于1-酰基-GPC酰基转移酶的Km值（5.0微摩尔）。在最佳条件下，1-酰基-GPI与花生四烯酰辅酶A的酰化速率比与油酰辅酶A和亚油酰辅酶A的酰化速率高2-6倍，而与饱和脂肪酰辅酶A的酰化速率非常低。1-酰基-GPI与各种酰基辅酶A的酰化速率与1-酰基-GPC的酰化速率不同。这些结果表明，1-酰基-GPI的再酰化途径参与了花生四烯酸在血小板微粒体中掺入磷脂酰肌醇的过程。此外，凝血酶激活对人血小板中1-酰基-GPI和1-酰基-GPC酰基转移酶的酰基辅酶A特异性没有显著影响。
