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首页> 外文期刊>Biochemistry >EVIDENCE FOR ASSOCIATION OF AN ATP-STIMULATABLE CA2+-INDEPENDENT PHOSPHOLIPASE A(2) FROM PANCREATIC ISLETS AND HIT INSULINOMA CELLS WITH A PHOSPHOFRUCTOKINASE-LIKE PROTEIN
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EVIDENCE FOR ASSOCIATION OF AN ATP-STIMULATABLE CA2+-INDEPENDENT PHOSPHOLIPASE A(2) FROM PANCREATIC ISLETS AND HIT INSULINOMA CELLS WITH A PHOSPHOFRUCTOKINASE-LIKE PROTEIN

机译：胰岛和HIT胰岛素瘤细胞与磷酸果糖样蛋白缔合的ATP可刺激的独立于Ca2 +的磷酸酶A（2）的证据

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Glucose-induced insulin secretion from pancreatic islets requires metabolism of glucose within islet beta-cells, and ATP has attracted interest as a messenger of glucose metabolism within beta-cells. Glucose-induced insulin secretion from islets and HIT insulinoma cells is accompanied by activation of an ATP-stimulatable Ca2+-independent phospholipase A(2) (ASCI-PLA(2)) enzyme, the catalytic activity of which resides in a 40 kDa protein. An analogous PLA(2) enzyme in myocardium was recently found to consist of a complex of a 40 kDa catalytic protein with a tetramer of an isoform of the glycolytic enzyme phosphofructokinase (PFK). Association of the PFK isoform with the myocardial PLA(2) catalytic protein was found to confer ATP sensitivity onto the enzyme complex. Here we demonstrate that the majority of HIT cell and islet ASCI-PLA(2) catalytic activity elutes from a gel filtration column in a region corresponding to 400 kDa, suggesting that the 40 kDa beta-cell ASCI-PLA(2) catalytic protein exists as part of a larger molecular mass complex. Islet and HIT cell ASCI-PLA(2) activities were immunoprecipitated by antibodies directed against PFK, and the immunoprecipitates contained 40 and 85 kDa proteins which correspond to the molecular masses of the PLA(2) catalytic protein and of a PFK monomer, respectively. Islet and HIT cell ASCI-PLA(2) activities were selectively and reversibly adsorbed to affinity matrices containing immobilized PFK but not to similar matrices containing immobilized transferrin or bovine serum albumin. Addition of free PFK prevented binding of HIT cell ASCI-PLA(2) activity to immobilized PFK matrices and promoted desorption of activity previously bound to such matrices. These results suggest that beta-cell ASCI-PLA(2), like the myocardial enzyme, exists as a complex comprised of a catalytic protein and a PFK-like protein and raise the possibility that the ASCI-PLA(2) complex may represent a component of the beta-cell glucose sensor, which links glycolysis, phospholipid hydrolysis, and membrane electrochemical events involved in glucose-induced insulin secretion.
机译：胰岛的葡萄糖诱导的胰岛素分泌需要胰岛β细胞内的葡萄糖代谢，而ATP已引起人们的兴趣，因为它是β细胞内葡萄糖代谢的信使。胰岛和HIT胰岛素瘤细胞的葡萄糖诱导的胰岛素分泌伴随着ATP刺激性Ca2 +依赖性磷脂酶A（2）（ASCI-PLA（2））酶的活化，其催化活性位于40 kDa的蛋白质中。最近发现心肌中的类似PLA（2）酶由40 kDa催化蛋白与糖酵解磷酸果糖激酶（PFK）异构体的四聚体的复合物组成。 PFK亚型与心肌PLA（2）催化蛋白的关联被发现赋予酶复合物ATP敏感性。在这里，我们证明了大多数HIT细胞和胰岛ASCI-PLA（2）催化活性从对应于400 kDa的区域的凝胶过滤柱上洗脱，表明存在40 kDa的β-细胞ASCI-PLA（2）催化蛋白。作为较大分子量复合物的一部分。 Islet和HIT细胞的ASCI-PLA（2）活性通过针对PFK的抗体进行免疫沉淀，并且该免疫沉淀物分别含有40和85 kDa的蛋白质，分别对应于PLA（2）催化蛋白和PFK单体的分子量。 Islet和HIT细胞ASCI-PLA（2）活性被选择性地和可逆地吸附到含有固定化PFK的亲和基质上，而不吸收到含有固定化转铁蛋白或牛血清白蛋白的类似基质上。游离PFK的添加阻止了HIT细胞ASCI-PLA（2）活性与固定的PFK基质结合，并促进了以前与此类基质结合的活性的解吸。这些结果表明，像心肌酶一样，β细胞ASCI-PLA（2）作为由催化蛋白和PFK样蛋白组成的复合物存在，并增加了ASCI-PLA（2）复合物可能代表一种β细胞葡萄糖传感器的一部分，它与糖诱导的胰岛素分泌相关的糖酵解，磷脂水解和膜电化学事件相关。

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