Glucose Oxidase from Aspergillus niger, Type X-S, lyophilized powder, 100,000-250,000 units/g solid (without added oxygen)

Synonym: ß-D-Glucose:oxygen 1-oxidoreductase, G.Od., GOx

CAS Number: 9001-37-0

EC Number: 232-601-0

Enzyme Commission (EC) Number: 1.1.3.4

MDL Number: MFCD00131182

Analysis Note
Protein determined by biuret

Application
Glucose oxidase is widely used in the food and pharmaceutical industries¹ as well as a major component of glucose biosensors.²

Biochem/physiol Actions
Glucose oxidase catalyses the oxidation of ß-d-glucose to d-glucono-ß-lactone and hydrogen peroxide, with molecular oxygen as an electron acceptor.^3,4

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

Unit Definition
One unit will oxidize 1.0 µmole of ß-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%.

General description
Molecular Weight: 160 kDa (gel filtration)
pI: 4.2
Extinction coefficient: E1% = 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 ß-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 ß-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 ß-D-glucose, solutions of D-glucose can be quantified as a-D-glucose will mutorotate to ß-D-glucose as the ß-D-glucose is consumed by the enzymatic reaction.