Grigg M E, Gounaris K, Selkirk M E
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London, UK.
Biochem J. 1996 Jul 15;317 ( Pt 2)(Pt 2):541-7. doi: 10.1042/bj3170541.
Nippostrongylus brasiliensis, a small nematode parasite of the gastrointestinal tract of rodents, secretes an enzyme that cleaves the proinflammatory molecule platelet-activating factor to its inactive lyso-form. The enzyme activity of Ca(2+)-dependent and does not exhibit interfacial activation. It does not require the addition of reducing agents for maximal activity, and is not inhibited by thiol-active reagents. Sensitivity of inhibitors suggests the involvement of serine and histidine residues in the enzyme activity. As described for other platelet-activating factor acetylhydrolases, it cannot cleave, nor is it inhibited by, long-chain diacyl phospholipids that are typical substrates for phospholipases A2. The purified enzyme was resolved by SDS/PAGE as a heterodimer composed of two protein subunits with apparent molecular masses of 38 and 25 kDa. The properties of the nematode enzyme thus differ from those described for the mammalian enzymes, but are more closely related to those of an acetylhydrolase than a phospholipase.
巴西日圆线虫是啮齿动物胃肠道的一种小型线虫寄生虫，它分泌一种酶，该酶可将促炎分子血小板活化因子裂解为无活性的溶血形式。该酶的活性依赖于Ca(2+)，且不表现出界面活化。它不需要添加还原剂即可达到最大活性，也不受硫醇活性试剂的抑制。抑制剂的敏感性表明丝氨酸和组氨酸残基参与了酶的活性。正如其他血小板活化因子乙酰水解酶的描述一样，它不能裂解典型的磷脂酶A2底物长链二酰基磷脂，也不受其抑制。纯化后的酶经SDS/PAGE分析为异二聚体，由两个表观分子量分别为38 kDa和25 kDa的蛋白质亚基组成。因此，线虫酶的特性与哺乳动物酶的特性不同，但与乙酰水解酶的特性更密切相关，而不是与磷脂酶的特性相关。
