Dey C S, Majumder G C
Biochem Biophys Res Commun. 1987 Jul 31;146(2):422-9. doi: 10.1016/0006-291x(87)90546-8.
Phosphatidyl inositol has been found to inhibit strongly the activity of a cyclic AMP-independent protein kinase located on the external surface of goat epididymal intact spermatozoa. Phosphatidyl inositol at a concentration as low as 10 micrograms/ml inhibited nearly 50% of the ecto-kinase activity for the phosphorylation of the exogenous protein substrate: casein. Phosphatidyl ethanolamine at a relatively high concentration (125 micrograms/ml) inhibited slightly (approx 25%) the activity of the enzyme whereas other phospholipids: phosphatidyl serine and choline, diacyl glycerol, phosphatidic acid and myo-inositol-2-phosphate had no appreciable effect on the kinase activity. Phosphatidyl inositol has also served as a potent inhibitor of the phosphorylation of sperm ecto-phosphoproteins by the endogenous kinase activity of intact spermatozoa. By thin layer chromatography it has been shown that the observed inhibitory effect of the phospholipid was not due to any impurities or degraded products of phosphatidyl inositol. Phosphatidyl inositol inhibited the kinase activity noncompetitively with respect to casein and Mg2+ but uncompetitively with respect to ATP. The results raised the possibility that phosphatidyl inositol-mediated high affinity inhibition of protein kinase(s), may constitute a novel mechanism for the regulatory actins of the phospholipid in mammalian cells.
已发现磷脂酰肌醇能强烈抑制位于山羊附睾完整精子外表面的一种不依赖环磷酸腺苷的蛋白激酶的活性。浓度低至10微克/毫升的磷脂酰肌醇就能抑制近50%的胞外激酶活性，该活性负责使外源蛋白质底物酪蛋白发生磷酸化。相对高浓度（125微克/毫升）的磷脂酰乙醇胺对该酶的活性有轻微抑制作用（约25%），而其他磷脂，如磷脂酰丝氨酸、胆碱、二酰基甘油、磷脂酸和肌醇 - 2 - 磷酸对激酶活性没有明显影响。磷脂酰肌醇还能有效抑制完整精子的内源性激酶活性对精子胞外磷蛋白的磷酸化作用。通过薄层层析表明，观察到的磷脂抑制作用并非由于磷脂酰肌醇的任何杂质或降解产物所致。磷脂酰肌醇对酪蛋白和Mg2+而言以非竞争性方式抑制激酶活性，但对ATP而言以反竞争性方式抑制。这些结果增加了一种可能性，即磷脂酰肌醇介导的对蛋白激酶的高亲和力抑制作用，可能构成磷脂在哺乳动物细胞中调节作用的一种新机制。
