The S1 sub-site is where catalysis occurs in CPA, and the zinc ion is coordinated by Glu-72, His-69, and His-196 enzyme residues. A plane exists that bisects the active-site groove where residues Glu-270 and Arg-127 are on opposite sides of the zinc-water coupled complex.
In the S1 sub-site of CPA, catalysis occurs with the zinc ion coordinated by specific amino acid residues, including Glu-72, His-69, and His-196. A dividing plane is present in the active site that separates residues Glu-270 and Arg-127 on opposite sides of a zinc-water complex.