Inhibition of Scytalidium lignicolum acid protease B by 1-diazo-3-phenyl-2-propanone.

Abstract

The acid protease B from Scytalidium lignicolum, a pepstatin-insensitive acid protease, was modified with l-diazo-3-phenyl-2-propanone (DPP) in the presence of cupric ions. About 1 mol of DPP per mol of enzyme was incorporated with a concomitant loss of the activity. The modified enzyme was digested with thermolysin and DPP-labeled peptides were separated. One peptide, called SI, was purified and its amino acid sequence was found to be Ala-Thr-Ser-Asp-Thr-Ser-Gly-Ser, which corresponds to the sequence of residue Nos. 95 ~ 102 of the enzyme. Alkali treatment of the modified peptide resulted in complete removal of the modifier, suggesting that DPP is esterlinked to Asp-98 of the enzyme. The amino acid sequence around Asp-98 of the enzyme was significantly homologous to those around the active site aspartic acid residues of penicillopepsin and porcine pepsin. These results suggest that Asp 98 is one of the active site amino acids of the enzyme.