Studies on the oxidation reaction of tyrosine (Tyr) with H2O2 catalyzed by horseradish peroxidase (HRP) in alcohol–water medium by spectrofluorimetry and differential spectrophotometry

An oxidation reaction of tyrosine (Tyr) with H2O2 catalyzed by horseradish peroxidase (HRP) was studied by spectrofluorimetry and differential spectrophotometry in the alcohol(methanol, ethanol, 1-propanol and isopropanol)–water mutual solubility system. Compared with the enzymatic-catalyzed reaction in the water medium, the fluorescence intensities of the product weakened, even extinguished. Because the addition of alcohols made the conformation of HRP change, the catalytic reaction shifted to the side of polymerization and the polymer (AnH2, n ≥ 3) exhibited no fluorescence. The four alcohols cannot deactivate HRP. Moreover isopropanol activated HRP remarkably.