This is the peptidase domain of a D,L-carboxypeptidase. The active site residues are Arg86, Glu222 and the metal ligands, in the peptidase domain, are Gln46, Glu49 and His128 in UniProtKB:O25708. The protein binds many zinc ions and a calcium ion and there are other metal binding sites. The catalytic activity is the release of m-Dpm from the peptide muramyl-Ala-gamma-D-Glu-m-Dpm; this is probably the precursor of the cell wall cross-linking peptide [1].

1: Structural basis for the recognition of muramyltripeptide by Helicobacter pylori Csd4, a D,L-carboxypeptidase controlling the helical cell shape. Kim HS, Kim J, Im HN, An DR, Lee M, Hesek D, Mobashery S, Kim JY, Cho K, Yoon HJ, Han BW, Lee BI, Suh SW; Acta Crystallogr D Biol Crystallogr. 2014;70:2800-2812. PMID:25372672