Amine oxidase-like activity of polyphenols - Mechanism and properties

Polyphenols in several oxidation systems gained amine oxidase-like activity , probably due to the formation of the corresponding quinones. In the prese nce of Cu(II), o- and p-phenolic compounds exhibited amine oxidase-like act ivity, whereas only the o-phenolic compounds showed the activity in the pre sence of 1,1-diphenyl-2-picryihydrazyl radical. The activity was determined by measuring the conversion of benzylamine to benzaldehyde by HPLC. Moreov er, gallic acid, chlorogenic acid, and caffeic acid, which are plant polyph enols, converted the lysine residue of bovine serum albumin to alpha -amino -adipic semialdehyde residue, indicating lysyl oxidase-like activity. We al so characterized the activity of pyrocatechol, hydroquinone, and pyrogallol in the presence of Cu(II). The oxidative deamination was accelerated at a higher pH, and required O-2 and transition metal ions. Furthermore, EDTA ma rkedly inhibited the reaction but not beta -aminopropionitrile, which is a specific inhibitor of lysyl oxidase. Catalase significantly inhibited the o xidation, implying the participation of hydroxyl radical in the reaction, b ut superoxide dismutase stimulated the oxidation, probably due to its radic al formation activity. We discussed the mechanism of the oxidative deaminat ion by polyphenols and the possible significance of the activity for biolog ical systems.