|Family type peptidase||S81.001 - destabilase (Hirudo medicinalis), MEROPS Accession MER0003393 (peptidase unit: 23-133)|
|Content of family||Family S81 contains isopeptidases.|
Identifier created: MEROPS 9.8 (17 December 2012)|
Family S81 contains the bifunctional enzyme destabilase (S81.001) from the medicinal leech (Hirudo medicinalis) and other invertebrates. The family is also known as 'i-lyz' for 'invertebrate lysozyme'.
|Active site residues||S49 K58 |
|Active site||Destabilase has two active sites each with a different catalytic activity, that of a lysozyme and that of an isopeptidase. Mutagenesis studies have shown that the lysozyme activity is dependent upon Glu14 and Asp26, whereas the isopeptidase activity requires a serine/lysine catalytic dyad, namely Ser29 and Lys38 (Zavalova et al., 2012).|
|Activities and specificities||As a lysozyme, destabilase cleaves the beta-(1,4)-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine of the peptidoglycan of bacterial cell walls. The isopeptidase activities include hydrolysing epsilon-(gamma-Glu)-Lys crosslinks between Glu and Lys in a stabilized fibrin (Baskova & Nikonov, 1991) and similar isopeptide bonds found in the cross-linking peptide of peptidoglycan in bacterial cell walls (Joskova et al., 2009).|
|Molecular structure||The tertiary structure of lysozyme from Tapes japonica has been determined, and shows that the enzyme exists at low salt concentrations as a dimer. At high salt concentrations, monomers form and the chitinase activity increases (Goto et al., 2007).|