Barley chitinase, bacterial chitosanase, and lysozymes from goose (GEWL), phage (T4L) and hen (HEWL) all hydrolyse related polysaccharides. The proteins share no significant amino-acid similarities, but have a structurally invariant core consisting of two helices and a three-stranded β-sheet which form the substrate-binding and catalytic cleft. These enzymes represent a superfamily of hydrolases which are likely to have arisen by divergent evolution. Based on structural criteria, we divide the hydrolase superfamily into a bacterial family (chitosanase and T4L) and a eucaryotic family represented by chitinase and GEWL. Both families contain the core but have differing N- and C-terminal domains. Inclusion of chitinase and chitosanase in the superfamily suggests the archetypal catalytic mechanism of the group is an inverting mechanism. The retaining mechanism of HEWL is unusual.
ASJC Scopus subject areas
- Structural Biology