Kawasaki T, Snyder F
Biochim Biophys Acta. 1987 Jul 13;920(1):85-93. doi: 10.1016/0005-2760(87)90314-6.
A Ca2+-dependent lysophospholipase D activity in microsomal preparations from the rabbit kidney medulla hydrolyzes the choline moiety from 1-O-[9,10-3H]hexadecyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PAF) to form 1-O-[9,10-3H]hexadecyl-2-lyso-sn-glycero-3-P; the latter is subsequently dephosphorylated by a phosphohydrolase to 1-O-[9,10-3H]hexadecyl-sn-glycerol. Sodium vanadate, which is known to inhibit phosphohydrolases, reduces the proportion of hexadecylglycerol and increases the formation of hexadecyl-lysoglycerophosphate. Essentially no hydrolysis occurs when the sn-2 position of the hexadecyllysoGPC substrate contains an acyl moiety. The lysophospholipase D in rabbit kidney is of microsomal origin and has a broad pH optimum between 8.0 and 8.8, with the activity decreasing sharply from pH 7.6 to 7.2. Wykle et al. (Biochim. Biophys. Acta 619 (1980) 58-67) have previously demonstrated the existence of a microsomal lysophospholipase D (specific for ether lipid substrates) in rat tissues that requires Mg2+ and exhibits a pH optimum of 7.2; high activities of the Mg2+-dependent lysophospholipase D were found in liver and brain, but not in kidney. In contrast to the Mg2+-dependent lysophospholipase D in rat tissues, the renal enzyme from rabbits requires Ca2+ (5 mM), whereas Mg2+ (5 mM) exhibits little stimulatory action. Under optimal assay conditions (0.1 M Tris-HCl (pH 8.4)/5 mM CaCl2), lysophospholipase D in the rabbit kidney medulla has an activity of 2.7 nmol/min per mg protein compared to 0.9 nmol/min per mg protein for the lysophospholipase D in the rat kidney medulla (0.1 M Tris-HCl (pH 7.2)/5 mM MgCl2). The Ca2+-dependent lysophospholipase D is highest in the liver and kidney medulla from rabbits, but is very low in rat tissues; similar activities were found in male and female rabbits. Our data indicate that the divalent metal ion requirements for expression of maximum lysophospholipase D activities can differ markedly among animal species and also suggest the microsomal Ca2+-dependent lysophospholipase D is an important catabolic route for lyso-PAF metabolism in rabbit renomedullary tissue.
兔肾髓质微粒体制剂中一种依赖钙离子的溶血磷脂酶D活性，可将1-O-[9,10-³H]十六烷基-2-溶血-sn-甘油-3-磷酸胆碱（溶血血小板活化因子）中的胆碱部分水解，形成1-O-[9,10-³H]十六烷基-2-溶血-sn-甘油-3-磷酸；后者随后被一种磷酸水解酶去磷酸化，生成1-O-[9,10-³H]十六烷基-sn-甘油。已知能抑制磷酸水解酶的钒酸钠，会降低十六烷基甘油的比例，并增加十六烷基溶血甘油磷酸的生成。当十六烷基溶血甘油磷酸胆碱底物的sn-2位含有酰基部分时，基本上不发生水解。兔肾中的溶血磷脂酶D起源于微粒体，在pH 8.0至8.8之间有较宽的最适pH值，从pH 7.6降至7.2时活性急剧下降。Wykle等人（《生物化学与生物物理学报》619 (1980) 58 - 67）此前已证实在大鼠组织中存在一种微粒体溶血磷脂酶D（对醚脂底物具有特异性），该酶需要镁离子，最适pH值为7.2；在肝脏和大脑中发现了高活性的依赖镁离子的溶血磷脂酶D，但在肾脏中未发现。与大鼠组织中依赖镁离子的溶血磷脂酶D不同，兔的肾酶需要钙离子（5 mM），而镁离子（5 mM）几乎没有刺激作用。在最佳测定条件下（0.1 M Tris - HCl（pH 8.4）/5 mM氯化钙），兔肾髓质中的溶血磷脂酶D活性为每毫克蛋白2.7 nmol/分钟，而大鼠肾髓质中的溶血磷脂酶D活性为每毫克蛋白0.9 nmol/分钟（0.1 M Tris - HCl（pH 7.2）/5 mM氯化镁）。依赖钙离子的溶血磷脂酶D在兔的肝脏和肾髓质中活性最高，但在大鼠组织中活性很低；在雄性和雌性兔中发现了相似的活性。我们的数据表明，不同动物物种中溶血磷脂酶D最大活性表达所需的二价金属离子需求可能有显著差异，这也表明微粒体依赖钙离子的溶血磷脂酶D是兔肾髓质组织中溶血血小板活化因子代谢的一条重要分解途径。
