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:
- Intron maturase
- Putative mitochondrial processing peptidase alpha subunit
- Superoxide dismutase [Mn] (EC 22.214.171.124)
- Asparagine synthetase [glutamine-hydrolysing] 3 (EC 126.96.36.199)
- Glucose-6-phosphate isomerase (EC 188.8.131.52)
Human proteins containing this domain
- Rawlings ND, Barrett AJ (1995). "Evolutionary families of metallopeptidases". Meth. Enzymol. 248: 183–228. doi:10.1016/0076-6879(95)48015-3. PMID 7674922.
- Osterman AL, Grishin NV, Smulevitch SV, Zagnitko OP, Matz MV, Stepanov VM, Revina LP (1992). "Primary structure of carboxypeptidase T: delineation of functionally relevant features in Zn-carboxypeptidase family". J. Protein Chem. 11 (5): 561–570. doi:10.1007/bf01025034. PMID 1449602.
- Lipscomb WN, Rees DC, Lewis M (1983). "Refined crystal structure of carboxypeptidase A at 1.54 A resolution". J. Mol. Biol. 168 (2): 367–387. doi:10.1016/S0022-2836(83)80024-2. PMID 6887246.
- Huber R, Guasch A, Coll M, Aviles FX (1992). "Three-dimensional structure of porcine pancreatic procarboxypeptidase A. A comparison of the A and B zymogens and their determinants for inhibition and activation". J. Mol. Biol. 224 (1): 141–157. doi:10.1016/0022-2836(92)90581-4. PMID 1548696.