InterPro domain: IPR002933

This group of proteins contains the metallopeptidases and non-peptidase homologues (amidohydrolases) that belong to the MEROPS peptidase family M20 (clan MH) [ 1 ]. The peptidases of this clan have two catalytic zinc ions at the active site, bound by His/Asp, Asp, Glu, Asp/Glu and His. The catalysed reaction involves the release of an N-terminal amino acid, usually neutral or hydrophobic, from a polypeptide [ 2 ]. The peptidase M20 family has four subfamilies:

• M20A - type example, glutamate carboxypeptidase from Pseudomonas sp. RS16 ( P06621 )
• M20B - type example, peptidase T from Escherichia coli ( P29745 )
• M20C - type example, X-His dipeptidase from E. coli ( P15288 )
• M20D - type example, carboxypeptidase Ss1 from Sulfolobus solfataricus ( P80092 )

Homologues from the family that are not peptidases include:

• Acetylornithine deacetylase, which releases an acetyl group and L-ornithine from N(2)-acetyl-L-ornithine [ 2 ]
• N-acetyldiaminopimelate deacetylase, which catalyses the conversion of N-acetyl-diaminopimelate to diaminopimelate and acetate [ 3 ]
• N-carbamoyl-L-amino-acid hydrolase, which converts D,L-5-monosubstituted hydantoins into D- or L-amino acids [ 4 ]
• Aminoacylase-1, which hydrolyses N-acylated or N-acetylated amino acids [ 5 ]
• Succinyl-diaminopimelate desuccinylase ( 3.5.1.18 ), which catalyses the hydrolysis of N-succinyl-L,L-diaminopimelic acid, forming succinate and LL-2,6-diaminoheptanedioate (DAP, a component of bacterial cell walls) [ 6 ]

1. Evolutionary families of metallopeptidases. Meth. Enzymol. 248, 183-228
2. Mechanistic analysis of the argE-encoded N-acetylornithine deacetylase. Biochemistry 39, 1285-93
3. Bacterial distribution of the use of succinyl and acetyl blocking groups in diaminopimelic acid biosynthesis. J. Bacteriol. 101, 323-4
4. Cloning and sequencing of the genes involved in the conversion of 5-substituted hydantoins to the corresponding L-amino acids from the native plasmid of Pseudomonas sp. strain NS671. J. Bacteriol. 174, 962-9
5. Essential roles of zinc ligation and enzyme dimerization for catalysis in the aminoacylase-1/M20 family. J. Biol. Chem. 278, 44496-504
6. Bacterial N-succinyl-L-diaminopimelic acid desuccinylase. Purification, partial characterization, and substrate specificity. J. Biol. Chem. 263, 1622-7