| Type: | Family | Name: | Peptidase M23A, B-lytic metalloendopeptidase |
| 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 [].B-lytic endopeptidases are bacterial metallopeptidases that belong to MEROPS peptidase family M23 (clan M-), subfamily M23A. Cleavage is specific for glycine bonds, especially in -Gly-Gly+Xaa sequences (Xaa is any aliphatic hydrophobic residue). They lyse the cell walls of Gram positive bacteria in which thepeptidoglycan cross-links contain glycine residues. The enzymes contain zinc, but the exact position of the metal-binding ligands is uncertain. Onthe basis of similarity with D-Ala-D-Ala-carboxypeptidase, it has been suggested that a conserved His-X-His motif (where X is any amino acid)forms part of the binding site [].The enzyme from Achromobacter lyticusis synthesised as a 374 aa precursor. The N-terminal 195 residues are removed to leave the mature enzyme of 179 residues []. This entry also includes protease LasA from Pseudomonas aeruginosa. LasA is involved in proteolysis and elastolysis []. | Short Name: | Pept_M23A_Blytic |
