Purification and Characterization of Cellobiose Dehydrogenase from Irpex lacteus and Its Adsorption on Cellulose

Abstract

White-rot fungus Irpex lacteus produces two cellobiose dehydrogenases (CDH I and CDH II) which have different electron acceptor specificity. CDH II which is a major CDH produced by I. lacteus was purified about 262 times to homogeneity and characterized. CDH II was a hemoflavo protein with the molecular mass of 97 kDa on SDS-PAGE, and it was a glycoprotein with carbohydrate content of 7.2% as glucose. Optimum temperature, heat stability as well as substrate specificity of this enzyme were similar to CDH from Phanerochaete chrysosporium. However, the stable pH range of CDH II was pH 3 to 5, which was different from other CDHs reported (pH 4 to 10). Cellobiose and cytochrome c were the best substrate and electron acceptor with kcat/Km values of 429.4- and 4405 mM-1s-1, respectively. From the studies on adsorption isotherm of this enzyme on cellulose, the one-binding site mechanism was suggested. Moreover, CDH II had higher adsorption affinity but lower adsorption capacity on crystalline cellulose than on amorphous one.