Portland State University. Department of Chemistry
Date of Publication
Master of Science (M.S.) in Chemistry
Polyphenol oxidase, Pear
1 online resource (2, iii, 35 leaves)
Polyphenolases (O-diphenol: O₂ oxidoreductase E.C. 188.8.131.52) have been isolated from a wide variety of plant and animal sources. This work deals with the isolation and characterization of polyphenolase from a previously unreported source, Pyrus communis, the common pear, horticultural variety D'Anjou. The chronometric method of assay was used, in which the enzymic oxidation of the substrate, usually catechol, is coupled to the oxidation of ascorbic acid and the time required to oxidize a specific amount of substrate is noted as the time required to colorize an external startch-iodide indicator. Various methods of isolation and purification were attempted. After a suitable isolation procedure was established, the enzyme was characterized by its substrate specificity, and its sensitivity to temperature, pH and inhibitors. Pear polyphenolase was characterized in particulate and soluble forms. The enzyme differs from other reported catechol oxidases in that it does not oxidize monophenols. A new spectrophotometric assay is described.
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Tracy, Mary Ellen, "Pear polyphenolase" (1970). Dissertations and Theses. Paper 688.