Isolation and Amino Acid Sequence of a Peptide Containing an Epoxide-Reactive Residue from the Thermolysin-Digest of Scytalidium lignicolum Acid Protease B

抄録

Scytalidium lignicolum acid protease B, a pepstatin-insensitive acid protease, was modified by 1, 2-epoxy-3-(p-nitrophenoxy)propane (EPNP) with the concomitant loss of its enzyme activity, and an EPNP-labeled peptide was isolated from the thermolysin-digest of the modified enzyme by HPLC. The amino acid sequence of the peptide was determined to be Ile-Leu-Glu-Thr-Gly, which corresponds to the sequence of residue Nos. 51-55 of the enzyme. The results of treatment of the labeled peptide with hydroxylamine suggested that the EPNP moiety is ester-linked to G1u⁵³ of the enzyme. The amino acid sequence around Glu⁵³ of the acid protease B showed high homology with those around the active site Asp residues of calf chymosin and porcine pepsin. These results show that it is highly possible that Glu⁵³ of the acid protease B is one of the amino acid residues involved in its catalytic activity.