<p>This domain identifies a number of eukaryotic carboxypeptidases, these include carboxypeptidase D, E (H), N, X, X2 and Z. These are metallopeptidases belong to MEROPS peptidase family M14 (clan MC), subfamily M14B.</p><p> Carboxypeptidase D (CPD) is a new B-type metallocarboxypeptidase that is membrane bound and has an acidic pH optimum. A hydrophobic region at the N terminus represents the signal peptide, and one near the C terminus that probably represents the transmembrane anchor. A regulatory domain within the protein has been identified as a beta-sandwich, comprising 7 strands in 2 sheets in a greek-key topology. Some family members have an additional 1-2 strands to the common fold [<cite idref="PUB00010644"/>].</p><p>The bacterial and archaeal sequences having this signature are variously annotated, examples are:</p><p> <ul><li>Hypothetical/conserved/membrane/cell surface protein </li><li>N-acetylglucosamine deacetylase</li><li>Side tail fibre protein homologue from lambdoid prophage Rac</li><li>Hypothetical tonB-linked outer membrane receptor</li><li>OmpA-related protein</li><li>Putative outer membrane protein, probably involved in nutrient binding</li><li>TonB-dependent receptor</li></ul> </p>