Glucose Oxidase, A. niger (EC 1.1.3.4.)

Since its discovery as an "antibiotic" (shown subsequently to be due to peroxide formation) there has been an interest in glucose oxidase, chiefly because of its utility in glucose estimation. For most clinical work the crude form of the A. niger enzyme has been satisfactory. However, it contains trace amount of polysaccharidases such as amylase, maltase and sucrase which can contribute to falsely high glucose levels. The purified enzyme is free of these traces and is recommended for analytical use in the presence of di-or polysaccharides. Glucose analytical systems employ the enzyme utilizing H2O2 production reacting with Fe(CN)-in the presence of luminol to produce luminescence proportional to the initial glucose concentration. Composition: The enzyme consists of two identical polypeptide chain subunits (80kD) covalently linked by disulfide bonds. Each subunit contains one mole of Fe and one mole of FAD (flavin-adenine dinucleotide). The molecule is approximately 74% protein, 16% neutral sugar and 2% amino sugars. FAD is replaceable with FHD (flavin-hypoxanthine dinucleotide) without loss of activity. Synonyms: EC=1.1.3.4, GOx, Notatin, Glucose oxyhydrase, Beta-D-glucose, Oxygen 1-oxidoreductaase, CAS No: 9001-37-0, Molecular Weight: 160kD, Source: Aspergillus niger, Form: Supplied as a dialyzed, lyophilized powder, Purity: Chromatographically purified, Activity: ~250u/mg (~300u/mg Protein), Unit Definition: 1 unit oxidizes 1umole of o-dianisidine per minute at 25ºC, pH 6.0. Assay Method: The reaction velocity is determined by an increase in absorbance at 460 nm resulting from the oxidation of o-dianisidine through a peroxidase coupled system. One unit causes the oxidation of one micromole of o-dianisidine per minute at 25°C and pH 6.0 under the conditions specified. Quality Control: SDS-PAGE, Catalase: <3u/mg Protein, Amylase: <0.2%, Saccharase: <0.2%, Maltase: <0.2%, Optimum pH: 5.5 with broad range 4-7, Specificity: The enzyme is highly specific for beta-D-glucose. The alpha anomer is not acted upon, 2-deoxy-D-glucose, D-mannose and D-galactose exhibit low activities as substrate. Inhibitors: Ag+, Hg2+, Cu2+. FAD binding is inhibited by several nucleotides. Storage and Stability: Stable for 12 months at 2-8°C. Dry preparations are stable for years when stored cold. Solutions are reasonably stable under a variety of conditions.