Vinokurov K S, Elpidina E N, Oppert B, Prabhakar S, Zhuzhikov D P, Dunaevsky Y E, Belozersky M A
Department of Entomology, Biological Faculty, Moscow State University, Moscow 119992, Russia.
Comp Biochem Physiol B Biochem Mol Biol. 2006 Oct;145(2):126-37. doi: 10.1016/j.cbpb.2006.05.005. Epub 2006 May 23.
The spectrum of Tenebrio molitor larval digestive proteinases was studied in the context of the spatial organization of protein digestion in the midgut. The pH of midgut contents increased from 5.2-5.6 to 7.8-8.2 from the anterior to the posterior. This pH gradient was reflected in the pH optima of the total proteolytic activity, 5.2 in the anterior and 9.0 in the posterior midgut. When measured at the pH and reducing conditions characteristic of each midgut section, 64% of the total proteolytic activity was in the anterior and 36% in the posterior midgut. In the anterior midgut, two-thirds of the total activity was due to cysteine proteinases, whereas the rest was from serine proteinases. In contrast, most (76%) of the proteolytic activity in the posterior midgut was from serine proteinases. Cysteine proteinases from the anterior were represented by a group of anionic fractions with similar electrophoretic mobility. Trypsin-like activity was predominant in the posterior midgut and was due to one cationic and three anionic proteinases. Chymotrypsin-like proteinases also were prominent in the posterior midgut and consisted of one cationic and four anionic proteinases, four with an extended binding site. Latent proteinase activity was detected in each midgut section. These data support a complex system of protein digestion, and the correlation of proteinase activity and pH indicates a physiological mechanism of enzyme regulation in the gut.
在黄粉虫幼虫中肠蛋白质消化的空间组织背景下，研究了其消化蛋白酶的谱。中肠内容物的pH从前向后从5.2 - 5.6增加到7.8 - 8.2。这种pH梯度反映在总蛋白水解活性的最适pH中，前肠为5.2，后肠为9.0。在每个中肠段特有的pH和还原条件下测量时，总蛋白水解活性的64%在前肠，36%在后肠。在前肠中，总活性的三分之二归因于半胱氨酸蛋白酶，其余来自丝氨酸蛋白酶。相反，后肠中大部分（76%）的蛋白水解活性来自丝氨酸蛋白酶。前肠的半胱氨酸蛋白酶由一组具有相似电泳迁移率的阴离子组分代表。类胰蛋白酶活性在后肠中占主导地位，由一种阳离子和三种阴离子蛋白酶引起。类胰凝乳蛋白酶在后肠中也很突出，由一种阳离子和四种阴离子蛋白酶组成，其中四种具有扩展的结合位点。在每个中肠段都检测到了潜在的蛋白酶活性。这些数据支持了一个复杂的蛋白质消化系统，蛋白酶活性与pH的相关性表明了肠道中酶调节的生理机制。
