The carboxypeptidase A family can be divided into two subfamilies: carboxypeptidase H (regulatory) and carboxypeptidase A (digestive). Members of the H family have longer C-termini than those of family A, and carboxypeptidase M (a member of the H family) is bound to the membrane by a glycosylphosphatidylinositol anchor, unlike the majority of the M14 family, which are soluble.
The zinc ligands have been determined as two histidines and a glutamate, and the catalytic residue has been identified as a C-terminal glutamate, but these do not form the characteristic metalloprotease HEXXH motif. Members of the carboxypeptidase A family are synthesised as inactive molecules with propeptides that must be cleaved to activate the enzyme. Structural studies of carboxypeptidases A and B reveal the propeptide to exist as a globular domain, followed by an extended alpha-helix; this shields the catalytic site, without specifically binding to it, while the substrate-binding site is blocked by making specific contacts.
Other examples of protein families in this entry include:
Human proteins containing this domain.
AEBP1; AGBL1; AGBL2; AGBL3; AGBL4; AGBL5; AGTPBP1; CPA1; 
CPA2; CPA3; CPA4; CPA5; CPA6; CPB1; CPB2; CPD; 
CPE; CPM; CPN1; CPO; CPXM1; CPXM2; CPZ;
References.
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