The bond in a substrate where hydrolysis occurs is known as the 'scissile bond'. In the Schechter and Berger nomenclature (14) , residues on the left-hand side of the scissile bond (towards the N-terminus) are numbered P1, P2, P3, etc. and residues on the right-hand side (towards the C-terminus) are numbered P1 0 , P2 0 , P3 0 , etc. with cleavage occurring between P1 and P1 0 . The substrate-binding pocket in the peptidase that accommodates the P1 residue is known as the S1 pocket, and that accommodating the P1 0 residue is the S1 0 pocket.