STUDIES ON INHIBITION OF MUSHROOM POLYPHENOL OXIDASE USING CHLOROGENIC ACID AS SUBSTRATE

The inhibitory effects of aromatic acids of the benzoic, cinnamic, and phenylalkanoic series on the enzymatic activity of a commercial purif ied mushroom polyphenol oxidase (PPO), using chlorogenic acid as a sub strate, were determined by spectrophotometric and polarographic method s. The I50 values obtained were higher when determined by the polarogr aphic method. Hydroxylation and methylation of the benzene ring as wel l as the addition of a second methylene group adjacent to the carboxyl ic acid decreased the inhibitory effect. Aromatic acids of the benzoic and cinnamic series appeared to have, respectively, an irreversible a nd most often a reversible inhibitory effect on PPO activity. The resu lts also showed that the aromatic acids exhibited noncompetitive, mixe d, and uncompetitive types of inhibition, with a range of K(i) values varying from 0.26 to 56.7 mM. Spectrophotometric and polarographic met hods failed to determine the type of inhibition for protocatechuic, ca ffeic, hydroxyphenylacetic, and hydroxyphenylpropionic acids. Benzoic, o-coumaric, m-coumaric, ferulic, phenylacetic, and phenylpropionic ac ids demonstrated different types of inhibition depending upon the meth od used. The results indicated that the type and degree of inhibitory effect of aromatic carboxylic acids are dependent upon both inhibitor and method used.