A Comparison of Chlorogenic Acid and Catechol as Substrates for the Polyphenol Oxidase from Tobacco and Mushroom.

It is reported that chlorogenic acid is widely distributed in plants (7) and is the principle polyphenol in tobacco leaves (8). When the tissues of the tobacco plant are injured, the polyphenols are oxidized and then polymerize, forming a brown pigment. This oxidation is reported to be catalyzed by polyphenol oxidase. Polyphenol oxidase has been identified in many species of plants and the enzyme from potato (3) and mushroom (2) has been investigated in some detail. In most cases the activity of the enzyme has been assayed by determination of the rate of oxidation of catechol using direct or indirect methods. Dawson et al (1) have presented curves indicating that rates of oxygen uptake in the presence of tobacco leaf extracts were greater when chlorogenic acid was used as a substrate than when either catechol or caffeic acid were utilized. These workers, however, did not indicate the concentrations of catechol or caffeic acid used. During the course of this investigation, it was found that the rate of oxidation of chlorogenic acid in the presence of a crude tobacco root extract was about 5-fold greater than the rate of oxidation of catechol. Conversely, the rate of oxidation of catechol catalyzed by a crude mushroom extract was about 6.5-fold greater than that with chlorogenic acid. The enzymes from both sources have been partially purified to determine whether or not more than one polyphenol oxidase was present in each of the extracts.