Kumar S, Pritchard D I
Department of Life Science, University of Nottingham, University Park, U.K.
Int J Parasitol. 1992 Aug;22(5):563-72. doi: 10.1016/0020-7519(92)90003-4.
Following the observation that live third-stage larvae (L3) could digest gelatin in vitro, gelatinolytic protease activity has been demonstrated at pH 8.5, in both exsheathing fluid (EF) and excretory/secretory (ES) products of infective L3 of Necator americanus. EF resolved as a single band of proteolytic activity, with a mol. wt of 116 kDa, while L3 ES products exhibited multiple bands of proteolysis, at 219, 200, 195, 166, 137, 92, 72 and 62 kDa; weak bands were detectable at 92 and 72 kDa. The EF protease was characterized as cysteine, whereas ES apparently possessed one serine (195 kDa) and seven (219, 200, 166, 137, 92, 72 and 62 kDa) cysteine protease bands and a combination of metallo- and cysteine proteases of approximately the same mol. wts (62, 137 and 219 kDa). Though EF was not able to cleave immunoglobulins, ES was shown to cleave IgG, IgA and IgM, but not IgD or IgE. The activity appeared to be directed toward the Fc portion of the molecule, and was inhibited by PMSF, which is indicative of serine protease activity. The significance of the presence of such apparently diverse proteases in larval products is discussed.
在观察到活的第三期幼虫（L3）能够在体外消化明胶之后，已证明美洲板口线虫感染性L3的脱鞘液（EF）和排泄/分泌（ES）产物在pH 8.5时具有明胶分解蛋白酶活性。EF表现为单一的蛋白水解活性条带，分子量为116 kDa，而L3 ES产物表现出多条蛋白水解条带，分子量分别为219、200、195、166、137、92、72和62 kDa；在92和72 kDa处可检测到弱条带。EF蛋白酶被鉴定为半胱氨酸蛋白酶，而ES显然具有一条丝氨酸蛋白酶（195 kDa）和七条半胱氨酸蛋白酶条带（219、200、166、137、92、72和62 kDa）以及分子量大致相同（62、137和219 kDa）的金属蛋白酶和半胱氨酸蛋白酶的组合。虽然EF不能切割免疫球蛋白，但ES可切割IgG、IgA和IgM，但不能切割IgD或IgE。该活性似乎针对分子的Fc部分，并被PMSF抑制，这表明存在丝氨酸蛋白酶活性。本文讨论了幼虫产物中存在如此明显多样的蛋白酶的意义。
