THE ROLES AND FUNCTION OF CELLULOSE-BINDING DOMAINS

Most cellulolytic enzymes consist of distinct catalytic and cellulose- binding domains (CBDs). Similar domain structures are also found in en zymes degrading other insoluble carbohydrates such as raw starch and c hitin. Such binding domains improve the binding and facilitate the act ivity of the catalytic domain on the insoluble but not on soluble subs trates, Based on their amino acid sequence similarities, the CBDs have been divided into several different families. Structure determination and subsequent mutagenesis studies have revealed that CBDs rely on se veral aromatic amino acids for binding to the cellulose surfaces. The CBDs binding to crystalline cellulose have different topologies but sh are similar rigid backbone structures for correct positioning of the s ide chains required for the substrate recognition and binding. CBDs re present ideal affinity tags for specific immobilisation of various oth er proteins to cellulose. Furthermore, improved understanding and cont rol of their action will be important for the improvement of the biote chnological value of cellulolytic enzymes. (C) 1997 Elsevier Science B .V.