Determination of glucose oxidase activity by tyrosine fluorescence spectrophotometry

A novel Fe²⁺/Tyr/H₂O₂ fluorescence reaction system has been established for the purpose of analyzing glucose oxidase activity. This system involves the catalysis of glucose oxidase on glucose to produce H₂O₂, which in turn oxidizes tyrosine to a highly fluorescent substance under the catalysis of Fe²⁺. The fluorescence intensity is subsequently employed to ascertain the enzymatic activity of glucose oxidase. The enzymatic oxidation reaction and tyrosine fluorescence reaction conditions were optimized based on the H₂O₂ standard curve equation. Direct fluorescence spectrophotometry was used to determine the activity range and detection limit of glucose oxidase, which were found to be 7.00 × 10^-5-7.00 × 10^-2 U/mL and 3.36 × 10^-5 U/mL (Enzyme-like activity is 6.72 × 10^-4 U/mL, The enzyme reaction time is 5 min), respectively, with a relative standard deviation of less than 3.2 %. This method has been successfully applied to determine the activity of glucose oxidase in food additives, with a recovery rate ranging from 96.00 % to 102.0 %.