Description
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 β-D-glucose with a KM 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.
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Mass of glucose oxidase (GOX), a flavoprotein ranges from approximately 130 to 175 kDa. Some fungi and insects are capable of producing GOX.
Application
Glucose oxidase is widely used in the food and pharmaceutical industries as well as a major component of glucose biosensors.
Glucose Oxidase from Aspergillus niger has been used:
in the (glucose oxidase) GO reagent to measure the glucose content by the glucose oxidase (GO) method
to activate the human renal carcinoma cell line for constructing the oxidative stress model
to study its influence in the paste on the analytical performance of the bioelectrode
Biochem/physiol Actions
Glucose oxidase catalyses the oxidation of β-d-glucose to d-glucono-β-lactone and hydrogen peroxide, with molecular oxygen as an electron acceptor.
Glucose oxidase (GOX) oxidizes D-glucose to D-gluconolactone and hydrogen peroxide. Hydrogen peroxide, the catalytic product of GOX, serves as an anti-bacterial and anti-fungal agent. It is safe and can be used in several industrial applications like baking, dry egg powder production, wine production, gluconic acid production, etc. It possesses electrochemical activity, which makes it extremely important in glucose sensors and in fuel cell applications.
Analysis Note
May contain traces of amylase, maltase, glycogenase, invertase, and galactose oxidase.
Protein determined by biuret
Other Notes
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%.
