Bacterial 1,3-1,4-beta-glucanases: structure, function and protein engineering.

1,3-1,4-beta-Glucanases (or lichenases, EC 3.2.1.73) hydrolyse linear beta-glucans containing beta-1,3 and beta-1,4 linkages such as cereal beta-glucans and lichenan, with a strict cleavage specificity for beta-1,4 glycosidic bonds on 3-O-substituted glucosyl residues. The bacterial enzymes are retaining glycosyl hydrolases of family 16 with a jellyroll beta-sandwich fold and a substrate binding cleft composed of six subsites. The present paper reviews the structure-function aspects of the enzymatic action including mechanistic enzymology, protein engineering and X-ray crystallographic studies.