Catalase inhibition an anti cancer property of flavonoids: A kinetic and structural evaluation.

Flavonoids are dietary polyphenols that present abundantly in fruits and vegetables. Flavonoids have inhibitory effects on enzymes and catalase is one among them. Catalase is a common enzyme ubiquitously found in all living organisms exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide to water and oxygen (2H2O2→2H2O+O2). Inhibition of pure and cellular catalase from K562 cells by flavonoids was similar and exhibited the following efficacy; Myrecetin>Quercetin>Kaempferol and Quercetin>Luteolin>Apigenin demonstrating structure activity relationship. Circular Dichroism (CD) spectra have shown distinct loss in α-helical structure of the catalase on interaction with the flavonoids. All flavonoids inhibited the catalase activity by uncompetitive mechanism. The Km and Vmax values of pure catalase were observed to be 294mM-1 and 0.222mM-1s-1 respectively and on inhibition with myrecetin the values decreased to a minimum of 23mM-1 and 0.014mM-1s-1 respectively. Inhibition of catalase will directly results in increased production of Reactive Oxygen Species (ROS) and pro-oxidant property of flavonoids. This inhibition was reversed in presence of Cu2+ ions because of the chelating affect of flavonoids.