Enzymatic characterization of anionic trypsin of the catfish (Parasilurus asotus).

An anionic trypsin, isolated from the pancreatic extract of the catfish (Parasilurus asotus), had a pH optimum of 8.3 for the hydrolysis of N-tosyl-L-arginine methyl ester. The enzyme was most stable at pH 6.0-8.5, and was stabilized by calcium ions. The enzyme was inhibited by typical trypsin inhibitors including some serine proteinase inhibitors. Km and kcat values of the enzyme for N-tosyl-L-arginine methyl ester and N-tosyl-L-lysine methyl ester were quite similar to those of bovine cationic trypsin.