| Type: | Family | Name: | Peptidase M38, beta-aspartyl dipeptidase |
| Description: | 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 []. 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 [].This group of proteins include metallopeptidases belonging to the MEROPS peptidase family M38 (clan MJ, beta-aspartyl dipeptidase family). This entry includes the beta-aspartyl dipeptidase from Escherichia coli, (, IadA), which degrades isoaspartyl dipeptides and may unblock degradation of proteins that cannot be repaired. This entry also describes closely related proteins from other species (e.g. Clostridium perfringens, Thermoanaerobacter tengcongensis) that may have an equivalent in function. This family shows homology to dihydroorotases. The L-isoaspartyl derivative of Asp arises non-enzymatically over time as a form of protein damage. In this isomerisation, the connectivity of the polypeptide changes to pass through the beta-carboxyl of the side chain. Much but not all of this damage can be repaired by protein-L-isoaspartate (D-aspartate) O-methyltransferase. | Short Name: | Pept_M38_dipep |
