On the Nature of the Enzyme Catechol Oxidase in Tea Plants

The enzyme catechol oxidase plays a key role in the manufacture of black tea. It is responsible for most, if not for all, of the chemical reactions which take place during tea fermentation. For this reason much research has been, and con tinues to be, devoted to the elucidation of the properties of this enzyme. Until recently, it was generally believed that the enzyme was insoluble in nature and the available evidence was inter­ preted to indicate that the enzyme was insoluble because it was bound to some cell parti­ culates; probably the chloroplasts. A recent discovery has provided strong evidence which suggests that the enzyme is, in fact, soluble in nature. Further, it has been shown that the polyphenolic compounds present in the tissues of tea shoot tips cause all the soluble proteins (enzymes) to precipitate as soon as the organisation of these tissues is destroyed; and this is exactly what happens when these tissues are homogenized for the purpose of extracting the enzymes present ina cell free state or when flush is rolled in orthodox tea manufacture to bring about fermentation. These new findings suggest that the previous reports that the enzyme catechol oxidase was insoluble were due to the artifact caused by the precipitation of all soluble proteins in the tissues of tea shoot tips caused by the polyphenolic compounds which arc present. A method for the extraction of soluble catechol oxidase from tea tissues has been developed and it is described in this report. The method is based on the inclusion of an insoluble polyphenol absorbant in the enzyme media. This additive is effective because it is able to absorb the polyphenols from solution before they are able to interact with the proteins presen t and cause them to precipitate.