Yamashita Atsushi, Kamata Ryo, Kawagishi Norikazu, Nakanishi Hiroki, Suzuki Hiroshi, Sugiura Takayuki, Waku Keizo
Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-0195.
J Biochem. 2005 May;137(5):557-67. doi: 10.1093/jb/mvi067.
The phospholipase A2s (PLA2s) are a diverse group of enzymes that hydrolyze the sn-2 fatty acid from phospholipids and play a role in a wide range of physiological functions. A 61-kDa calcium-independent PLA2, termed cPLA2gamma, was identified as an ortholog of cPLA2alpha with approximately 30% overall sequence identity. cPLA2gamma contains a potential prenylation motif at its C terminus, and is known to have PLA2 and lysophospholipase activities, but its physiological roles have not been clarified. In the present study, we expressed various forms of recombinant cPLA2gamma, including non-prenylated and non-cleaved forms, in order to investigate the effects of C-terminal processing. We examined the expression of the wild type and non-prenylated (SCLA) forms of cPLA2gamma, and found that the SCLA form was expressed normally and retained almost full activity. Expression of the prenylated and non-cleaved form of cPLA2gamma using yeast mutants lacking prenyl protein proteases AFC1 (a-factor-converting enzyme) and RCE1 (Ras-converting enzyme) revealed decreased expression in the mutant strain compared to that in the wild type yeast, suggesting that complete C-terminal processing is important for the functional expression of cPLA2gamma. In addition, cPLA2gamma was found to have coenzyme A (CoA)-independent transacylation and lysophospholipid (LPL) dismutase (LPLase/transacylase) activities, suggesting that it may be involved in fatty acid remodeling of phospholipids and the clearance of toxic lysophospholipids in cells.
磷脂酶A2（PLA2）是一类多样的酶，可水解磷脂的sn-2脂肪酸，并在广泛的生理功能中发挥作用。一种61 kDa的钙非依赖性PLA2，称为cPLA2γ，被鉴定为cPLA2α的直系同源物，总体序列同一性约为30%。cPLA2γ在其C末端含有一个潜在的异戊二烯化基序，已知具有PLA2和溶血磷脂酶活性，但其生理作用尚未阐明。在本研究中，我们表达了各种形式的重组cPLA2γ，包括未异戊二烯化和未切割的形式，以研究C末端加工的影响。我们检测了cPLA2γ野生型和未异戊二烯化（SCLA）形式的表达，发现SCLA形式正常表达并保留了几乎全部活性。使用缺乏异戊二烯化蛋白蛋白酶AFC1（α因子转化酶）和RCE1（Ras转化酶）的酵母突变体表达cPLA2γ的异戊二烯化和未切割形式，发现与野生型酵母相比，突变菌株中的表达降低，这表明完整的C末端加工对于cPLA2γ的功能表达很重要。此外，发现cPLA2γ具有不依赖辅酶A（CoA）的转酰基作用和溶血磷脂（LPL）歧化酶（LPLase/转酰基酶）活性，这表明它可能参与磷脂的脂肪酸重塑以及细胞中有毒溶血磷脂的清除。
