Glucose Oxidase from Aspergillus niger, 10ku

Glucose oxidase is an FAD-containing glycoprotein. The enzyme is specific for β-D-glucose. O can be replaced by hydrogen acceptors such as 2,6-dichlorophenol indophenol. 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. 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. 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. One unit of glucose oxidase is the activity which causes the liberation of 1 micromole of glucose per minute at 25°C and pH 7.0 under the specified conditions.