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REPRINTS, COPIES
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Properties and Localization
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Polyphenol oxidases catalyze the oxidation of phenolic compounds in the presence of molecular oxygen. Polyphenol oxidases have copper in the prosthetic group. The copper content of mushroom polyphenol oxidase, for example, is 0.2 percent and it appears in univalent form (Kertesz, 1966).
The official name of polyphenol oxidase is (1.10.3.1)ortho-diphenol: oxygen oxidoreductase as recommended by the Commission on Enzymes of the International Union of Biochemists (1961) |
Polyphenol oxidases have multiple components (Constantinides and Bedford, 1967). These multiple forms may result from configurational changes in the protein molecule or from different combinations or degrees of polymerization of one or more subunits (Jolley and Mason, 1965). Mathew and Parpia (1971) suggested that each form may be bound to a specific site within a subcellular structure where it fulfills a specific role. Harel et al. (1964, 1965) found that apple polyphenol oxidase occurred in both the chloroplast and the mitochondrial fractions. Specificty of substrate and value of Michaelis constant differed for the two fractions. A soluble fraction of the enzyme was also identified. They found that the soluble fraction of apple polyphenol oxidase increased and the particulate fraction degreased with ripening. This suggested that the enzyme was released from the organelles during ripening. Walker and Hulme (1966) questioned the association of the enzyme with particulate fractions of the cell, suggesting that this was an artifact of extraction procedure.
Updated: Wednesday, June 20, 2007. |
