A serine endopeptidase with a molecular mass of 25 kDa has been purified from the culture filtrate of Trichoderma viride to electrophoretic homogeneity. The isoelectric point was determined at 7.3. Two carboxyl sites at Arg22 and Lys29 of the oxidized insulin B-chain were cleaved, and peptidyl-p-nitroanilide substrates with Lys or Arg at the P1 position were also hydrolyzed by the enzyme. These results suggest that the specificity of T. viride protease is similar to that of trypsin.
However, the hydrolytic activity toward casein of T viride protease was less than that of porcine trypsin. The amino-terminal sequence of the enzyme protein is similar to that of bovine trypsin. It seems that the trypsin of T viride is a protease which is promising for the substitution of animal trypsin in the food industry and in medicine at this stage.