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

1,3-1,4-beta -Glucanases (or lichenases, EC 3.2.1.73) hydrolyse linear B-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. (C) 2000 Elsevier Science B.V. All rights reserved.