Inactivation of creatine kinase induced by quercetin with horseradish peroxidase and hydrogen peroxide. pro-oxidative and anti-oxidative actions of quercetin.

Pro-oxidative and anti-oxidative actions of quercetin were examined through inactivation of CK and inhibition of lipid peroxidation. Quercetin induced inactivation of creatine kinase (CK) during the interaction with horseradish peroxidase and hydrogen peroxide (HRP-H(2)O(2)). CK activity in heart homogenate was also reduced by quercetin with HRP-H(2)O(2). Flavonoids that have a catechol structure in the B ring, such as taxifolin, catechin and luteolin, also induced CK inactivation. These flavonoids strongly inhibited NADPH and ADP-Fe(3+)-dependent microsomal lipid peroxidation. These results suggest a close relationship between pro-oxidative and anti-oxidative actions of quercetin. Electron spin resonance (ESR) signals of the quercetin radical was emitted during the interaction of quercetin with HRP-H(2)O(2) in the presence of Zn(2+) as a stabilizer. Adding CK diminished the ESR signals of quercetin radicals, suggesting CK efficiently scavenged quercetin radicals. Sulfhydryl groups and tryptophan residues in CK decreased during the interaction of quercetin with HRP-H(2)O(2). The kinetic parameters of K(m) and V(max) for ADP and creatine phosphate changed rapidly, suggesting that the inactivation of CK was induced through conformational change of the enzyme. Glyceraldehyde-3-phosphate dehydrogenase had a higher sensitivity to quercetin with HRP-H(2)O(2) than CK. Quercetin radicals may mediate between pro-oxidative and anti-oxidative action.