The specificity of peptide bond cleavage of acid proteinase A from Aspergillus niger var. macrosporus toward oxidized ribonuclease A.

In order to investigate the specificity of peptide bond cleavage by acid proteinase A from Aspergillus niger var. macrosporus (Aspergillopepsin II), performic acid-oxidized bovine pancreatic ribonuclease A was digested by the enzyme at pH 1.8 or 5.5, and the resulting peptides were separated by HPLC and analyzed. Among the total 123 peptide bonds approximately thirty and thirteen bonds were cleaved at pH 1.8 for 2 h and at pH 5.5 for 20 h, respectively. Cleavages occurred fairly specifically at Tyr-X, Phe-X, His-X, Asn-X, Asp-X, Gln-X, and Glu-X bonds.