Partial characterization of digestive proteases in Totoaba (Totoaba macdonaldi)

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 degrees C and remained highly stable, while optimum temperature for intestinal proteases was 45 degrees C, with high stability between 35-55 degrees 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.