The P1 and P1′ Residue Specificities of Physarolisin I, a Serine-Carboxyl Peptidase from the True Slime Mold Physarum polycephalum

The P1 and P1′ residue specificities of physarolisin I were investigated using combinatorial peptide substrates. The results indicated that certain hydrophobic residues and acidic residues are preferred at the P1 position and some hydrophobic residues at the P1′ position. This P1 specificity, different from other serine-carboxyl peptidases, appears to be explained partially by the nature of the S1 subsite residues.