Electrophoretic Separation of the Phenolases from Potato Tubers

Abstract

EARLY investigations of the properties of polyphenol oxidase from plants showed that most preparations catalysed the oxidation of several polyphenolic substrates. In the past few years it has been demonstrated that crude polyphenol oxidase preparations actually are mixtures of several phenol oxidase proteins, each exhibiting unique catalytic and physical properties. Smith and Krueger² used a column of hydroxyl apatite and chromatographically separated crude extracts of mushrooms into a series of purified fractions. These contained several enzyme types, including the classical catecholase and cresolase enzymes. Sisler and Evans³ showed that chlorogenic acid was a better substrate for the crude polyphenol oxidase from tobacco than for a comparable preparation from mushrooms. The ratios of rates of oxidation of chlorogenic acid to rates of oxidation of catechol as catalysed by each of a series of purified extracts from tobacco varied widely, indicating the presence of more than one type of polyphenol oxidase enzyme. Uritani⁴ used starch-gel electrophoresis and separated crude extracts of sweet potato roots into three distinct bands each showing a capacity to catalyse the oxidation of chlorogenic acid. From these experiments it seems clear that organisms contain several types of polyphenol oxidase enzymes.