Glucose Oxidase from Aspergillus niger

Molecular Weight: 160 kDa (gel filtration)
pI: 4.2
Extinction coefficient: E^1% = 16.7 (280 nm)

Glucose oxidase from Aspergillus niger is a dimer consisting of 2 equal subunits with a molecular mass of 80 kDa each. Each subunit contains one flavin adenine dinulceotide moiety and one iron. The enzyme is a glycoprotein containing ~16% neutral sugar and 2% amino sugars. The enzyme also contains 3 cysteine residues and 8 potential sites for N-linked glycosylation.

Glucose oxidase is capable of oxidizing D-aldohexoses, monodeoxy-D-glucoses, and methyl-D-glucoses at varying rates.

The pH optimum for glucose oxidase is 5.5, while it has a broad activity range of pH 4-7. Glucose oxidase is specific for β-D-glucose with a K_M of 33-110 mM.

Glucose oxidase does not require any activators, but it is inhibited by Ag⁺, Hg²⁺, Cu²⁺, phenylmercuric acetate, and p-chloromercuribenzoate. It is not inhibited by the nonmetallic SH reagents: N-ethylmaleimide, iodoacetate, and iodoacetamide.

Glucose oxidase can be utilized in the enzymatic determination of D-glucose in solution. As glucose oxidase oxidizes β-D-glucose to D-gluconolactate and hydrogen peroxide, horseradish peroxidase is often used as the coupling enzyme for glucose determination. Although glucose oxidase is specific for β-D-glucose, solutions of D-glucose can be quantified as α-D-glucose will mutorotate to β-D-glucose as the β-D-glucose is consumed by the enzymatic reaction.

Several publications cite use of the G2133 glucose oxidase in their protocols and in various applications, such as the following:
a) Biosensor development:

• Diazoresin nanofilm coatings on alginate microspheres: Srivastava, R. et al., Biotechnol. Bioeng., 91(1), 124-131 (2005).
• Paper-based glucose biosensor: Lankelma, J. et al., Anal. Chem., 84(9), 417-4152 (2012)
• Microfluidic device with glucose oxidase immobilized on hydrogel for glucose analysis of blood: He, R.-Y. et al., RSC Adv., 9, 32367-32374 (2019).

b) Single-molecule FRET study of human RAD51 filament formation: Subramanyam, S. et al., Methods Enzymol., 600, 201-232 (2018).
c) Enzymatic fuel-cells with chitosan-based membranes: Bahar, T., and Yazici, M.S., Electroanalysis, 32(6), 1304-1314 (2020).

Glucose oxidase is widely used in the food and pharmaceutical industries as well as a major component of glucose biosensors.

Glucose oxidase catalyses the oxidation of β-d-glucose to d-glucono-β-lactone and hydrogen peroxide, with molecular oxygen as an electron acceptor.

May contain traces of amylase, maltase, glycogenase, invertase, and galactose oxidase.

One unit will oxidize 1.0 μmole of β-D-glucose to D-gluconolactone and H₂O₂ per min at pH 5.1 at 35 °C, equivalent to an O₂ uptake of 22.4 μl per min. If the reaction mixture is saturated with oxygen, the activity may increase by up to 100%.

Lyophilized powder containing phosphate buffer salts and sodium chloride

Protein determined by biuret.