The cleavage specificities of typical aspartic proteinases: pepsin A, gastricsin, cathepsin D and rhizopuspepsin,were examined at different pH values with oxidized insulin B chain as a substrate with special attention to the specificities near neutral pH. Significant differences in relative specificity for scissile bonds were observed between pH 2.0 and 5.5-6.5, which may be partly related with the changes in dissociation states of the His and Glu residues in the substrate and the ionizable residues in the active site of each enzyme.
Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.