Sarkis G J, Kurpiewski M R, Ashcom J D, Jen-Jacobson L, Jacobson L A
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260.
Arch Biochem Biophys. 1988 Feb 15;261(1):80-90. doi: 10.1016/0003-9861(88)90106-3.
Crude homogenates of the soil nematode Caenorhabditis elegans exhibit strong proteolytic activity at acid pH. Several kinds of enzyme account for much of this activity: cathepsin D, a carboxyl protease which is inhibited by pepstatin and optimally active toward hemoglobin at pH 3; at least two isoelectrically distinct thiol proteases (cathepsins Ce1 and Ce2) which are inhibited by leupeptin and optimally active toward Z-Phe-Arg-7-amino-4-methylcoumarin amide at pH 5; and a thiol-independent leupeptin-insensitive protease (cathepsin Ce3) with optimal activity toward casein at pH 5.5. Cathepsin D is quantitatively most significant for digestion of macromolecular substrates in vitro, since proteolysis is inhibited greater than 95% by pepstatin. Cathepsin D and the leupeptin-sensitive proteases act synergistically, but the relative contribution of the leupeptin-sensitive proteases depends upon the protein substrate.
土壤线虫秀丽隐杆线虫的粗匀浆在酸性pH值下表现出很强的蛋白水解活性。几种酶导致了大部分这种活性：组织蛋白酶D，一种羧基蛋白酶，被胃蛋白酶抑制剂抑制，在pH 3时对血红蛋白的活性最佳；至少两种等电点不同的巯基蛋白酶（组织蛋白酶Ce1和Ce2），被亮抑蛋白酶肽抑制，在pH 5时对Z-苯丙氨酸-精氨酸-7-氨基-4-甲基香豆素酰胺的活性最佳；以及一种不依赖巯基且对亮抑蛋白酶肽不敏感的蛋白酶（组织蛋白酶Ce3），在pH 5.5时对酪蛋白的活性最佳。组织蛋白酶D在体外对大分子底物的消化在数量上最为显著，因为胃蛋白酶抑制剂可使蛋白水解受到超过95%的抑制。组织蛋白酶D和对亮抑蛋白酶肽敏感的蛋白酶协同作用，但对亮抑蛋白酶肽敏感的蛋白酶的相对贡献取决于蛋白质底物。
