The action of inhibitors on the catechol oxidase of potatoes.

ATTEMPTS have been made to classify the phenolases into groups such as the catechol oxidases, tyrosinases, and laccases [Raper, 1928], but the classification is made difficult by the lack of satisfactory methods of characterising the enzymes [Onslow and Robinson, 1928]. The present work was undertaken with the object of testing whether the catechol oxidases of different origin behave similarly towards inhibitors, or whether they show any marked differences of behaviour which might be used as a further guide in classifying these enzymes. Catechol oxidases are found widely distributed in plants, fungi and insects. In the animal kingdom, a phenolase specific for 3: 4-dihydroxyphenylalanine (" Dopa oxidase ") and a phenolase of horse's heart muscle [Wieland and Lawson, 1931] have been investigated. Other systems effecting the oxidation of adrenaline and phenolases present in melaniferous tumours have been described. Summaries of the literature are given by Raper [1928], Onslow and Robinson [1928], Hizume [1924] and Oppenheimer and Kuhn [1931]. Resorcinol was chosen as a suitable inhibitor, since preliminary experiments with the catechol oxidase of potatoes showed that the inhibition with resorcinol appeared to be of a simple competitive type, as it could be reduced by increasing the substrate concentration. EXPERIMENTAL.