Tam S W, Man R Y, Choy P C
Can J Biochem Cell Biol. 1984 Dec;62(12):1269-74. doi: 10.1139/o84-161.
The hydrolysis of acyl esters in phosphatidylcholine and phosphatidylethanolamine by phospholipase A in hamster heart subcellular fractions was investigated. Phosphatidylcholine was found to be a much poorer substrate than phosphatidylethanolamine for the cardiac phospholipase A. The rate of hydrolysis of phosphatidylcholine by microsomal phospholipase A was 10-fold less than with phosphatidylethanolamine as substrate. When 1-[1-14C] palmitoyl-2-acyl phosphatidyl-[Me-3H]choline was used as substrate, both phospholipase A1 and A2 activities were detected in all subcellular fractions, but the highest specific activities for both enzymes were located in the microsomal fraction. However, phospholipase A2 activity in all hamster heart particulate fractions was three to six times higher than phospholipase A1 activity. The hydrolysis of phosphatidylcholine by microsomal phospholipase A2 displayed an alkaline pH optimum and an absolute requirement for Ca2+ or Mg2+. The enzyme also depicted high specificity towards polyunsaturated acyl groups at the C-2 position of phosphatidylcholine.
研究了仓鼠心脏亚细胞组分中磷脂酶A对磷脂酰胆碱和磷脂酰乙醇胺中酰基酯的水解作用。结果发现，对于心脏磷脂酶A而言，磷脂酰胆碱作为底物的效果远不如磷脂酰乙醇胺。微粒体磷脂酶A对磷脂酰胆碱的水解速率比对磷脂酰乙醇胺作为底物时低10倍。当使用1-[1-¹⁴C]棕榈酰-2-酰基磷脂酰-[甲基-³H]胆碱作为底物时，在所有亚细胞组分中均检测到了磷脂酶A1和A2的活性，但两种酶的最高比活性均位于微粒体组分中。然而，仓鼠心脏所有颗粒组分中的磷脂酶A2活性比磷脂酶A1活性高3至6倍。微粒体磷脂酶A2对磷脂酰胆碱的水解作用在碱性pH条件下表现出最佳活性，并且对Ca²⁺或Mg²⁺有绝对需求。该酶对磷脂酰胆碱C-2位的多不饱和酰基也表现出高度特异性。
