Some properties of cellobiose oxidase from the white-rot fungus Sporotrichum pulverulentum

Abstract

Cellobiose oxidase from the white-rot fungus Sporotrichum pulverulentum has been purified to homogeneity by a new procedure. The carbohydrate and amino acid compositions of the enzyme have been determined. Cellobiose oxidase contains FAD and cytochrome b prosthetic groups. Mr of the enzyme has been estimated at 74400 by sedimentation equilibrium. The enzyme is a monomer. Optical, fluorescence and e.p.r. spectra of oxidized and reduced cellobiose oxidase have been determined. A preliminary investigation of the substrate specificity of cellobiose oxidase reveals that disaccharides and even some insoluble polysaccharides are substrates, but not monosaccharides. Strong substrate inhibition is seen at high concentrations of cellobiose. This effect is particularly marked when oxygen is the electron acceptor. Cellobiose oxidase is unusual among flavoproteins, since it stabilizes the red anionic flavin semiquinone and forms a sulphite adduct, yet appears to produce the superoxide anion as its primary reduced oxygen product.