Abstract
The specificity of acid proteases from a strain of Scytalidium lignicolum was investigated using oxidized insulin B-chain.
These enzymes were considerably specific for the bonds involving aromatic or hydrophobic amino acid residues. These specificities were similar to those of usual acid proteases. However, acid proteases A-1 and A-2 specifically hydrolyzed Cys (7)-Gly (8) bond, and acid protease B Tyr (26)-Thr (27) bond; these peptide bonds were not attacked by any acid proteases ever studied.
As expected from the results of investigation using various synthetic peptides, acid proteases A-1, A-2, and B thus exhibited distinguishable specificity on the oxidized B-chain with the usual microbial acid proteases which were inactivated by specific inhibitors such as S-PI, DAN, and EPNP.
