Studies on aspartase VIII. Protease-mediated activation: comparative survey of protease specificity for activation and peptide cleavage.

The active species of aspartase from Escherichia coli is further 3-5 fold activated upon limited proteolysis with trypsin releasing carboxy-terminal peptides as reported previously (N. Yumoto, M. Tokushige, and R. Hayashi. Biochim. Biophys. Acta, 616, 319 (1980) ). Survey of the protease specificity for the activation revealed that subtilisin BPN' and several other proteases having far broader substrate specificity than trypsin also activated the enzyme. The results of sequence analyses revealed that subtilisin BPN' cleaved mainly the serylarginine bond near the carboxy-terminal and released an octapeptide, while trypsin cleaved mainly the arginyltyrosine bond which is just next to the subtilisin cleavage site. These results suggest that the protease-mediated activation does not necessarily require a site-specific peptidyl cleavage, but the cleavage of any bond within a certain region centered at arginine, the eighth residue from the carboxy-terminal, is sufficient.