cDNA cloning and expression of intracellular platelet-activating factor (PAF) acetylhydrolase II - Its homology with plasma PAF acetylhydrolase
cDNA cloning and expression of intracellular platelet-activating factor (PAF) acetylhydrolase II - Its homology with plasma PAF acetylhydrolase
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DOI：
10.1074/jbc.271.51.33032
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发表时间：
1996-12-20
影响因子：
4.8
通讯作者：
Inoue, K
中科院分区：
文献类型：
--
作者：
Hattori, K;Adachi, H;Inoue, K
血小板活化因子（PAF）乙酰水解酶通过去除sn-2位的乙酰基而使PAF失活，其广泛分布于血浆和组织中。我们先前证明组织胞质溶胶含有至少两种类型的PAF乙酰水解酶，亚型Ib和II，并且亚型Ib是包含45-、30-和29-kDa亚基的异源三聚体，在本研究中，我们分离了牛和人PAF乙酰水解酶亚型II的cDNA克隆，从克隆cDNA的最长开放阅读框，牛和人PAF乙酰水解酶II均含有392个氨基酸残基，在氨基酸水平上彼此相同，两种酶都含有脂肪酶和丝氨酸酯酶特征的Gly-X-Ser-X-Gly基序，同工型II cDNA在COS 7细胞中的表达导致PAF乙酰水解酶活性显着增加，使用针对牛酶的已建立的单克隆抗体进行的免疫印迹研究表明，重组蛋白存在于膜级分以及可溶级分中，异构体II在牛的肝脏和肾脏中表达最丰富，但在其他组织中也观察到低水平，从异构体II的cDNA推导的氨基酸序列与异构体Ib的任何亚基都没有同源性，然而有趣的是，其氨基酸序列与血浆PAF乙酰水解酶的氨基酸序列有41%的同源性，结合以往文献资料表明其底物特异性与血浆PAF乙酰水解酶相似，提示组织型同工酶II与血浆PAF乙酰水解酶可能具有共同的生理功能。
Platelet-activating factor (PAF) acetylhydrolase, which inactivates PAF by removing the acetyl group at the sn-2 position, is widely distributed in plasma and tissues, We previously demonstrated that tissue cytosol contains at least two types of PAF acetylhydrolase, isoforms Ib and II, and that isoform Ib is a heterotrimer comprising 45-, 30-, and 29-kDa subunits, whereas isoform II is a 40-kDa monomer.In this study, we isolated cDNA clones of bovine and human PAF acetylhydrolase isoform II, From the longest open reading frame of the cloned cDNAs, both bovine and human PAF acetylhydrolases II are predicted to contain 392 amino acid residues and to exhibit 88% identity with each other at the amino acid level, Both enzymes contain a Gly-X-Ser-X-Gly motif that is characteristic of lipases and serine esterases, Expression of isoform II cDNA in COS7 cells resulted in a marked increase in PAF acetylhydrolase activity, An immunoblot study using an established monoclonal antibody against the bovine enzyme revealed that the recombinant protein exists in the membranous fraction as well as the soluble fraction, Isoform II is expressed most abundantly in the liver and kidney in cattle, but low levels were also observed in other tissues, The amino acid sequence deduced from the cDNA of isoform II had no homology with any subunit of isoform Ib, Interestingly, however, the amino acid sequence of isoform II showed 41% identity with that of plasma PAF acetylhydrolase, Combined with previous data demonstrating that isoform II shows similar substrate specificity to plasma PAF acetylhydrolase, these results indicate that tissue type isoform II and the plasma enzyme may share a common physiologic function.