Novel Insights into the Inhibitory Mechanism of Kaempferol on Xanthine Oxidase

Abstract

Xanthine oxidase (XO), a key enzyme in purine catabolism, is widely distributed in human tissues. It can catalyze xanthine to generate uric acid and cause hyperuricemia and gout. Inhibition kinetics assay showed that kaempferol inhibited XO activity reversibly in a competitive manner. Strong fluorescence quenching and conformational changes of XO were found due to the formation of a kaempferol-XO complex, which was driven mainly by hydrophobic forces. The molecular docking further revealed that kaempferol inserted into the hydrophobic cavity of XO to interact with some amino acid residues. The main inhibition mechanism of kaempferol on XO activity may be due to the insertion of kaempferol into the active site of XO occupying the catalytic center of the enzyme to avoid the entrance of the substrate and inducing conformational changes of XO. In addition, luteolin exhibited a stronger synergistic effect with kaempferol than did morin at the lower concentration.

Inhibitory kinetics and mechanism of kaempferol on α-glucosidase

“…(2)-(4), the values of K i and a were calculated to be (1.31 ± 0.03) Â 10 À5 mol L À1 and 5.75 ± 0.02 (n = 3), respectively, which confirmed that kaempferol tended to be more easily and firmly bound to the free a-glucosidase rather than the a-glucosidase-sub strate complex (Phan et al, 2013;Zhang, Chen, Song, & Xie, 2006). Furthermore, the replots of slope and Y-intercept versus the concentration of kaempferol were linearly fitted, suggesting that this inhibitor had a single inhibition site or a single class of inhibition site on a-glucosidase (Wang et al, 2015). This result was consistent with that of above fluorescence titrations.…”

“…The replots of slope and Y-intercept versus [I] were linearly fitted, which suggested that there may be a single inhibition site or a single class of inhibition site (Wang, Zhang, Pan, & Gong, 2015). The kinetic data were analyzed using a computer program for linear regressions (Origin 8.0).…”

Dietary Flavonoids as Xanthine Oxidase Inhibitors: Structure–Affinity and Structure–Activity Relationships

“…10 Molecular Modeling. The molecular docking studies were carried out by the MGL tools 1.5.6 with AutoGrid4.0 and AutoDock4.0.…”

Screening of lipase inhibitors from Scutellaria baicalensis extract using lipase immobilized on magnetic nanoparticles and study on the inhibitory mechanism

“…Fluorescence quenching is a classical method to address such issue and has been widely used for probing the structure-affinity relationship in bindings of drugs to proteins [26,27]. It is particularly useful to explore the inhibitory mechanism of inhibitors on enzymes [28].…”