The aim of present study was to characterize the physicochemical and biochemical properties of trypsin from beluga Huso huso, a highly valuable sturgeon species. Trypsin, as an alkaline protease, is able to hydrolyze protein residues and peptides to release free amino acids and small peptides for intestinal absorption; therefore, the activity of trypsin has been widely used as a valuable indicator of digestive capacity in fish. The stability of trypsin was well-preserved at pH values from 6.0 to 11.0 and temperatures up to 50 °C. Optimum pH and temperature values for the enzyme were recorded at 8.5 and 55 °C by BAPNA (a specific substrate), respectively. According to the results obtained from the methods of casein-zymogram and inhibitory activity staining, the molecular weight of trypsin for beluga was 29.5 kDa. TLCK and SBTI, two specific trypsin inhibitors, showed a significant inhibitory effect on the enzymatic activity of the enzyme (p < 0.05). trypsin activity was significantly increased in the presence of Ca+2 and surfactants and decreased by oxidizing agents, Cu+2, Zn+2, and Co+2 (p < 0.05). However, univalent ions Na+ and K+ did not show any significant effect on the activity of the enzyme (p > 0.05). The results of our study show that the properties of trypsin from beluga are in agreement with data reported in bony fish and can contribute to the clear understanding of trypsin activity in this primitive species.
