ABSTRACT The objective of this study was to characterize the digestive proteases of totoaba (Totoaba macdonaldi). Fish were sacrificed to obtain the multienzymatic extracts from the stomach and intestine, and determine the stability and optimum pH and temperature values. Residual activity and number of isoforms were determined with some inhibitors. Optimal pH of stomach proteases was 2, with stability above 100% at that same pH. Optimum pH of intestinal proteases was between 9 and 11, with stability above 100% between 8-12. Optimum temperature for stomach proteases was 35°C and remained highly stable, while optimum temperature for intestinal proteases was 45°C, with high stability between 35-55°C. Pepstatin A totally inhibited acid protease activity and revealed a single band. SDS-PAGE zymogram revealed 8 bands in the intestine, where phenanthroline inhibited 80% of the total activity. The digestive capacity of T. macdonaldi is characteristic of a strict carnivore, similar to other marine fish species.

中文翻译：

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Totoaba (Totoaba macdonaldi) 消化蛋白酶的部分表征

摘要 本研究的目的是表征石首鱼 (Totoaba macdonaldi) 的消化蛋白酶。处死鱼以获得胃和肠的多酶提取物，并确定稳定性和最适pH值和温度值。用一些抑制剂测定残留活性和同种型的数量。胃蛋白酶的最佳 pH 值为 2，在相同 pH 值下稳定性高于 100%。肠道蛋白酶的最佳 pH 值在 9 到 11 之间，稳定性在 8-12 之间超过 100%。胃蛋白酶的最适温度为35°C并保持高度稳定，而肠蛋白酶的最适温度为45°C，在35-55°C之间具有高稳定性。胃蛋白酶抑制素 A 完全抑制酸性蛋白酶活性并显示出单条带。SDS-PAGE 酶谱显示肠中有 8 个条带，其中菲咯啉抑制了 80% 的总活性。T. macdonaldi 的消化能力是严格食肉动物的特征，类似于其他海洋鱼类。