Gallic acid oxidation by turnip peroxidase |
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Authors: | Mamdouh Y Kamel Nabil A Saleh Abdelhady M Ghazy |
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Institution: | National Research Centre, Biochemistry Laboratory, Cairo, Dokki, Egypt |
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Abstract: | Both ellagic and gallic acids non competitively inhibited guaiacol oxidation by turnip peroxidase. The Ki values were 3 and 26 μm for ellagic and gallic acid respectively. Enzymatic oxidation of gallic acid by the isolated major turnip peroxidase was characterized with respect to spectral behaviour, affinity constant and pH effect. The Km for H2O2 and gallic acid are 2.5 and 8.0 mM for turnip peroxidase. The pH optimum for gallic acid oxidation is about 6.5 and the rate constant k4 decreased with the increase of pH in presence of both guaiacol and Gallic acid. When the gallic acid oxidation products were subjected to chromatographic analysis, it was found to be converted mainly to ellagic and an unknown quinone. |
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Keywords: | Chenopodiaceae turnip peroxidases gallic acid ellagic acid |
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