Cellobiose oxidase

One of the cellobiose oxidoreductases present in S. pulverulentum has been characterised and named cellobiose oxidase (Ander and Eriksson, 1978). The enzyme contains both haem and flavin co factors and binds irreversibly to concanavalin A-Sepharose, suggesting that it is a glycoprotein. Cellobiose oxidase from S. pulverulentum has now been purified to homogeneity by Morpeth (1985). The carbohydrate and amino acid compositions of the enzyme have been determined. The enzyme contains FAD and cytochrome b prosthetic groups and is a monomer with an Mr of 74400 determined by sedimentation equilibrium. 

Disaccharides and even some insoluble polysaccharides are substrates, but not monosaccharides. Cellobiose oxidase is unusual among flavoproteins, as it stabilises the red anionic flavin semiquinone and forms a sulphite adduct, yet appears to produce the superoxide anion as its primary reduced oxygen product. 

The visible absorption spectrum of oxidised cellobiose oxidase is typical of cytochrome b (Fig. 5-15). The flavin in cellobiose oxidase is weakly fluorescent, with emission maxima at 564 nm and excitation maxima at 380 and 444 nm. There are no obvious transient changes on reduction that can be readily ascribed to flavin semiquinone, but the strong absorbance of the cytochrome would make such changes difficult to detect. 

Fig. 5-15. Absorption spectra of oxidised (curve 1) and reduced (curve 2) cellobiose oxidase. Reproduced with permission from Morpeth (1985).

Cellobiose Oxidases. — A recently discovered oxidative enzyme of importance in in vitro cellulose degradation seems to be a cellobiose oxidase. The contribution of this enzyme to the degradation has been discussed in a review of cellulose enzymolysis. 

Cellobiose Oxidases.—An extracellular enzyme which utilizes molecular oxygen to oxidise cellodextrins to the corresponding aldonic acids has been isolated from culture filtrates of the white rot fungus Sporotrichum pulveru-lentum. This enzyme, named cellobiose oxidase, was purified by classical techniques and was shown to be a glycoprotein (mol. wt. 9.3 x 10 ). The u.v. spectrum of the enzyme was characteristic of a haemoprotein, there being approximately one flavin component per enzyme molecule. The possible role of this complex enzyme in cellulose degradation was discussed. 

Carboxypeptidase Y Cathepsin D Cell lytic enzyme Cellobiose oxidase Cellulase... 

Cellobiose Oxidases.—The synthesis of an extracellular cellobiose oxidase (cellobiose dehydrogenase, cellobiose quinone oxidoreductase) parallels that of the cellulase activity when Chrysoporium lignorum and Polyporus versicolor... 

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