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Abstract: Mushrooms contain large quantities of tyrosinase (polyphenol oxidase, E.C. 1.10.3.1 orthodiphenol : oxidoreductase) which is responsible for brown pigment formation. Tyrosinase is characterized by two types of activity: (1) the oxidation of monophenols to the corresponding orthoquinones; and (2) the oxidation of ortho-diphenols to the corresponding orthoquinones. Rapid spectrophotometric methods have been used in the past to study diphenol oxidation but not monophenol oxidation. We present here the conditions that are required for the rapid spectrophotometric determination of monophenol (p-cresol) oxidation. Mushroom tyrosinase was partially purified by column chromatography. The enzyme was inhibited by substrate (p-cresol) and required a cofactor (4-methylcatechol). The molar extinction coefficient of 4-methylorthoquinone, product of the reaction, was 1.23 × 103 at 400 nanometer.
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