No abstract

Cellulose-degrading cultures of the white-rot fungus Phanerochaete chrysosporium produce two extracellular cellobiose-oxidizing enzymes, cellobiose oxidase and cellobiose:quinone oxidoreductase. These two enzymes bind strongly to microcrystalline cellulose (MCC) in the pH range 4-7; above neutral pH their affinity for MCC decreases. Cellulose-bound enzymes could not be eluted with phosphate buffer (20 mM, pH 6) containing polyols (10%), KC1 (1 M), urea (1 M) or 1% ionic or non-ionic detergent. TRIS or borate buffer at pH 9 eluted 30%-35% of the cellobiose-oxidizing enzyme activity. The celluloseimmobilized enzymes oxidized cellobiose actively, suggesting that the catalytic sites are not involved in cellulose binding. These results suggest that the cellobiose-oxidizing enzymes of P. chrysosporium may be organized into two domains: a cellulose-binding domain and a catalytic domain.