Comparative characterization of protease activity in cultured spotted rose snapper juveniles (Lutjanus guttatus)

Partial characterizations of digestive proteases were studied in three life stages of spotted rose snapper: early (EJ), middle (MJ) and late juvenile (LJ) with corresponding average weights of 21.3 +/- 2.6 g (3 months after hatching, MAH), 190 +/- 4.4 g (7 MAH), and 400 +/- 11.5 g (12 MAH). At sampling points, the digestive tract was dissected into the stomach (St), pyloric caeca (PC), and the intestine in three sections (proximal (PI), middle (MI) and distal intestine (DI)). The effect of pH and temperature and specific inhibitors were evaluated for acid and alkaline proteases. Total acid and alkaline protease activity showed a tendency to increase with juvenile life stage of fish while trypsin activity decreased. Differences were found in acid and alkaline protease activities at different pH and temperatures during juvenile stages. Pepstatin A inhibited total activity in the stomach extract in all juvenile stages. Activity in total alkaline protease inhibition was significantly higher in EJ using TLCK, PMSF, SBTI, Phen and Ovo than in MJ and LJ, while no significant differences were found with TPCK inhibition. Therefore increases in protease activities with fish growth through juvenile stages in which a substitution or diversification in the type of alkaline enzymes exist. These results lead a better comprehension of changes in digestive potential of Lutjanidae fish.