Specificity of an o-diphenol oxidase from Prunus avium fruits

Abstract

An o-diphenol oxidase extracted from sweet cherry fruits ( Prunus avium) was purified 17-fold, and the recovery of enzyme activity was 5·6%. The optimum pH with catechol as substrate was 4·2. The enzyme exhibited only catecholase activity and was inactive with monophenols. The specificity of the enzyme toward 19 substituted catechols was examined. Substituents in position 3 caused a decrease in the affinity for the enzyme, probably due to steric hindrance. Electron-donating substituents in position 4 enhanced enzymic activity, whereas electron-attracting substituents in the same position reduced or eliminated the oxidation.