Adamich M, Dennis E A
J Biol Chem. 1978 Jul 25;253(14):5121-5.
We have investigated the action and substrate specificity of phospholipase A2 (EC 3.1.1.4) purified from cobra venom (Naja naja naja) toward intact and Triton-solubilized human erythrocytes, toward ghost membranes, and toward extracted ghost lipids in mixed micelles with Triton X-100. We have found that: (i) phospholipids in the outer surface of intact erythrocytes are extremely poor substrates for the phospholipase, (ii) phospholipids in ghost erythrocyte membranes and in Triton-solubilized erythrocytes are suitable substrates for the enzyme, (iii) in these latter systems which contain a mixture of lipids, phosphatidylethanolamine is preferentially hydrolyzed, whereas in model studies on individual phospholipid species in mixed micelles with Triton, phosphatidylcholine is the preferred substrate of the enzyme, and (iv) the preferential hydrolysis of phosphatidylethanolamine is also observed for extracted ghost lipid mixtures in mixed micelles. These results demonstrate a dependence of phospholipase A2 activity on the ghosting procedure and a dependence of substrate specificity on the presence of other lipids. The relevance of these findings to the interpretation of membrane lipid asymmetry studies utilizing phospholipases is considered in detail.
我们研究了从眼镜蛇毒液（眼镜蛇指名亚种）中纯化得到的磷脂酶A2（EC 3.1.1.4）对完整的和经曲拉通增溶的人红细胞、对血影膜以及对与曲拉通X-100形成混合胶束的提取血影脂质的作用和底物特异性。我们发现：（i）完整红细胞外表面的磷脂是该磷脂酶极差的底物；（ii）血影红细胞膜和经曲拉通增溶的红细胞中的磷脂是该酶合适的底物；（iii）在这些含有脂质混合物的后一种体系中，磷脂酰乙醇胺优先被水解；而在对与曲拉通形成混合胶束的单个磷脂种类的模型研究中，磷脂酰胆碱是该酶的首选底物；（iv）在混合胶束中的提取血影脂质混合物中也观察到了磷脂酰乙醇胺的优先水解。这些结果表明磷脂酶A2活性对血影制备过程的依赖性以及底物特异性对其他脂质存在的依赖性。本文详细探讨了这些发现与利用磷脂酶解释膜脂质不对称性研究之间的相关性。
