Characterization of stomach and pyloric caeca proteinases of Tambaqui (Colossoma macropomum)

The effects of pH, temperature, inhibitors, and substrates on proteolytic activities of crude extracts from the stomach, liver, pyloric caeca, and intestines of Colossoma macropomum were investigated. The highest acid and alkaline proteolytic activities were found in stomach and pyloric caeca, respectively. The optimum pH for the acid and alkaline proteases were 1.8 and 7.0-9.0, respectively, while the optimum temperatures were 35C and 65C. This alkaline protease thermal stability remained unaltered after 90 min incubation at 55C. A pepsin-like protease was responsible for most of the acidic proteolytic activity (Pepstatin A inhibited approximately 90%), whereas PMSF inhibited about 40% of the alkaline protease. The alkaline proteolytic activity has attractive thermal properties for industrial applications.