1. The molecular weights of the glucose oxidases [EC 1.1.3.4] of Penicillium amagasakiense and Aspergillus Niger were measured by YPHANTIS' method and found to be 150,000 and 152,000, respectively.2. The carbohydrate and amino acid compositions in these enzymes were compared. Both enzymes contained the same kinds of carbo-hydrate, that is, mannose, glucose and hexosamine. There was more mannose and hexosamine and less glucose in the Aspergillus-enzyme than in the Penicillium-enzyme. There was more histidine, arginine and tyrosine and less lysine and phenylalanine in the Aspergillus-enzyme than in the Penicillium-enzyme.3. The two enzymes were titrated with D-glucose under anaerobic conditions, but no intermediate, such as a semiquinone or charge-transfer type compound, appeared in the equilibrium state between the oxidized and reduced forms. On titration with dithionite, an intermediate having a semiquinone character was formed with the Aspergillus-enzyme, but not with the Penicillium-enzyme. The absorption spectrum of the intermediate of the Aspergillus-enzyme was obtained on the basis of the value of the molecular extinction coefficient at each wavelength. The latter was calculated from the equilibrium relationship between the oxidized, semiquinone and reduced forms of the FAD moiety. © 1968 by the Journal of Biochemistry.
