Soubeyrand S, Lazure C, Manjunath P
Guy-Bernier Research Centre, 5415 Boulevard de L'Assomption, Montreal, Qu-ebec, Canada H1T 2M4.
Biochem J. 1998 Jan 1;329 ( Pt 1)(Pt 1):41-7. doi: 10.1042/bj3290041.
The major phospholipase A2 activity from bovine seminal plasma was recently purified [Soubeyrand, Khadir, Brindle and Manjunath (1997) J. Biol. Chem. 272, 222-227]. We here show that the 60 kDa enzyme is in fact a platelet-activating factor acetylhydrolase (PAF-AH). Sequences of the N-terminus as well as of internal fragments showed 100% identity with the cDNA-deduced sequences of bovine plasma PAF-AH. The enzyme has kinetic properties similar to those of the human serum PAF-AH. Although capable of hydrolysing long-chained phosphatidylcholine, it displayed a highly preferential activity towards PAF. The enzyme activity towards phosphatidylcholine, but not PAF, was Ca2+-dependent. Biochemical characterization revealed that the enzyme is extensively N-glycosylated and that it exists predominantly as a dimer in solution. Western blot analysis revealed that the enzyme is highly heterogeneous in charge, with a maximal distribution at an isoelectric point of approx. 5.7. The enzyme was expressed exclusively in the seminal vesicles and the ampulla. No association of the enzyme with either epididymal or ejaculated spermatozoa could be detected.
最近从牛精浆中纯化出了主要的磷脂酶A2活性物质[苏贝兰德、卡迪尔、布林德尔和马俊那斯（1997年）《生物化学杂志》272卷，222 - 227页]。我们在此表明，这种60 kDa的酶实际上是一种血小板活化因子乙酰水解酶（PAF - AH）。N端以及内部片段的序列与牛血浆PAF - AH的cDNA推导序列显示出100%的同一性。该酶具有与人血清PAF - AH相似的动力学特性。虽然它能够水解长链磷脂酰胆碱，但对PAF表现出高度优先的活性。对磷脂酰胆碱而非PAF的酶活性是Ca2 +依赖性的。生化特性表明该酶被广泛N - 糖基化，并且在溶液中主要以二聚体形式存在。蛋白质免疫印迹分析表明该酶在电荷方面高度异质，在约5.7的等电点处分布最为集中。该酶仅在精囊和壶腹表达。未检测到该酶与附睾精子或射出精子有任何关联。
