CELLULASES AND THEIR INTERACTION WITH CELLULOSE

Most effective cellulolytic enzymes are made of at least two constitutive domains, a catalytic domain and a non-catalytic cellulose-binding domain linked by a flexible peptide. There are several families of catalytic domains and of cellulose-binding domains resulting in a large number of their possible combinations. Removal of the cellulose-binding domain drastically reduces the binding capacity of cellulases to insoluble cellulose while the catalytic efficiency on soluble substrates Is usually maintained. Isolated cellulose-binding domains bear most of the binding properties of cellulases (quasi-irreversibility and dispersive effect) but do not hydrolyse cellulose. The multiple types of synergy that cellulases display when acting in combination on cellulose appear to result from their different activities and selectivity, from the substrate microheterogeneity, and sometimes from both.