ZnMc

Zinc-dependent metalloprotease		 ZnMc
SMART accession number:SM00235
Description: Neutral zinc metallopeptidases. This alignment represents a subset of known subfamilies. Highest similarity occurs in the HExxH zinc-binding site/ active site.
Interpro abstract (IPR006026):

In the MEROPS database peptidases and peptidase homologues are grouped into clans and families. Clans are groups of families for which there is evidence of common ancestry based on a common structural fold:

  • Each clan is identified with two letters, the first representing the catalytic type of the families included in the clan (with the letter 'P' being used for a clan containing families of more than one of the catalytic types serine, threonine and cysteine). Some families cannot yet be assigned to clans, and when a formal assignment is required, such a family is described as belonging to clan A-, C-, M-, N-, S-, T- or U-, according to the catalytic type. Some clans are divided into subclans because there is evidence of a very ancient divergence within the clan, for example MA(E), the gluzincins, and MA(M), the metzincins.
  • Peptidase families are grouped by their catalytic type, the first character representing the catalytic type: A, aspartic; C, cysteine; G, glutamic acid; M, metallo; N, asparagine; S, serine; T, threonine; and U, unknown. The serine, threonine and cysteine peptidases utilise the amino acid as a nucleophile and form an acyl intermediate - these peptidases can also readily act as transferases. In the case of aspartic, glutamic and metallopeptidases, the nucleophile is an activated water molecule. In the case of the asparagine endopeptidases, the nucleophile is asparagine and all are self-processing endopeptidases.

In many instances the structural protein fold that characterises the clan or family may have lost its catalytic activity, yet retain its function in protein recognition and binding.

Metalloproteases are the most diverse of the four main types of protease, with more than 50 families identified to date. In these enzymes, a divalent cation, usually zinc, activates the water molecule. The metal ion is held in place by amino acid ligands, usually three in number. The known metal ligands are His, Glu, Asp or Lys and at least one other residue is required for catalysis, which may play an electrophillic role. Of the known metalloproteases, around half contain an HEXXH motif, which has been shown in crystallographic studies to form part of the metal-binding site [(PUBMED:7674922)]. The HEXXH motif is relatively common, but can be more stringently defined for metalloproteases as 'abXHEbbHbc', where 'a' is most often valine or threonine and forms part of the S1' subsite in thermolysin and neprilysin, 'b' is an uncharged residue, and 'c' a hydrophobic residue. Proline is never found in this site, possibly because it would break the helical structure adopted by this motif in metalloproteases [(PUBMED:7674922)].

The majority of zinc-dependent metallopeptidases (with the notable exception of the carboxypeptidases) share a common pattern of primary structure [(PUBMED:2914602), (PUBMED:1894005)] in the part of their sequence involved in the binding of zinc, and can be grouped together as a superfamily,known as the metzincins, on the basis of this sequence similarity. They can be classified into around 40 distinct families [(PUBMED:7674922)].

This signature defines the metallopeptidases associated with MEROPS peptidase families: M7, M8, M10 (subfamilies A, B and C) and M12 (subfamily A) all of which are members of clan MA(M).

GO process:proteolysis (GO:0006508)
GO function:metallopeptidase activity (GO:0008237), zinc ion binding (GO:0008270)
Family alignment:
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There are 2939 ZnMc domains in 2924 proteins in SMART's nrdb database.

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