Partial Purification, Characterization and Investigation of Inhibitory Effects of Organic Compounds on Cinnamomum verum Polyphenoloxidase Enzymes

Polyphenol oxidase enzyme catalyzes oxidation of o-diphenol to o-quinone using molecular oxygen, while the final product unacceptably includes brown pigments. Therefore, inhibition of polyphenol oxidase is essential for the preservation of food products and vegetables. The enzyme is clinically beneficial for the treatment of dermal disorders with links to unusual darkening of the skin (hyper pigmentation) and is helpful in development of skincare products. The present study describes characterization and inhibition kinetics of the polyphenol oxidase from Cinnamomum verum fruit coat.

Purification and quantification of polyphenoloxidase were carried out using (NH4)2SO4 precipitation, dialysis with Sephadex G-100 column chromatography. The molecular weight was reported using SDS-PAGE. The Km and Vmax values were calculated using Lineweaver-Burk plot. The optimum pH, temperature and freeze-thaw were studied. Effects of several organic compounds on polyphenol oxidase activity were tested and IC50 values were calculated.

Polyphenol oxidase of Cinnamomum verum fruit coat has partially been purified as nearly 3.75-fold with an improvement of 4.58% using catechol as the substrate. The enzyme showed a single band with a molecular weight of approximately 66 kD. Optimal pH and temperature included 6.0 and 37°C, respectively. The Km and Vmax values included 1.67 Mm and 64.57 ∆A min-1, respectively. Inhibition type of cinnamic acid and ascorbic acid were uncompetitive while propyl benzoic acid showed a mixed type of inhibition. Thiol and chelating agents were strong inhibitors of enzyme activity. In conclusion, polyphenol oxidase can be used for the development of biosensors to detect and degrade phenolic compounds in industrial waste water.