Physicochemical properties of glucose oxidase

niger enzyme is a dimer with two very tightly bound coenzyme (FAD) molecules per dimer (Swoboda and Massey, 1965). The most salient properties of GOase are listed in Table 10.11. Only a small 

Number of subunits Coenzyme Overall structure Frictional ratio Stokes radius (nm) 

Carbohydrate content (mostly mannose) Isoelectric point Sedimentation coefficient (S) 

References a, Swoboda and Massey, 1965 b, Nakamura et al., 1976 c, Bentley, 1963. FAD = flavine adenine dinucleotide. 

Crystalline GOase retains its activity for at least two years at 0°C and 8 years at — 15°C (Bentley, 1963) and it is stable for at least a year in an (NH4)2S04 solution at 4°C. An aqueous solution of the enzyme is stable for a week at 5°C. Moreover, the activity of GOase is not affected at 39°C for 1 h at pH 5.6 or by incubation with 0.2% sodium deoxycholate or SDS, or with 1% pepsin or papain. The enzyme is unstable above 40°C or at pH values above 8, though the presence of glucose may exert a protective action. 

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