Enzymatic method for measuring the absolute value of oxygen concentration.
An enzymatic method for measuring the absolute concentration of oxygen in aqueous solutions, using 4-hydroxybenzoate 3-monooxygenase and glucose oxidase, is described. The monooxygenase is used for quantitative oxidation of 4-hydroxybenzoate and NADPH with oxygen into 3,4-dihydroxybenzoate and NADP+; the amount of oxygen can be measured as the amount of NADPH decreased by the reaction. The monooxygenase reaction is performed in a syringe, a closed system. After the completion of the monooxygenase reaction, glucose oxidase is added to the assay solution to consume the oxygen from the atmosphere; this enables us to measure the NADPH concentration in the solution spectrophotometrically in an open system and to check the anaerobicity of closed systems. The oxygen concentrations at 25 degrees C of oxygen-saturated and air-saturated water were 1.10 and 0.23 mM, respectively. The value for argon-bubbled water was zero within the experimental error; this justifies the assay system. Thus, it is shown that a sample containing 8 microM-1.1 mM oxygen can be measured by this method.
Department of Fermentation Technology, Faculty of Engineering, Osaka University.
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Yomo
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Urabe
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Okada
D001230:Aspergillus / Q000201:enzymology; D005949:Glucose Oxidase; D006899:Mixed Function Oxygenases; D009249:NADP; D010100:Oxygen / Q000032:analysis*; D011549:Pseudomonas / Q000201:enzymology
D009249:NADP; D006899:Mixed Function Oxygenases; D005949:Glucose Oxidase; C021385:3-hydroxybenzoate-4-monooxygenase; D010100:Oxygen