Inhibition kinetics and mechanism of genistein against α‐glucosidase

Abstract

Several studies have documented the effective inhibition of genistein, a component in soybeans against α‐glucosidase. However, the details of the inhibition mechanism and kinetics remain unfulfilled. Here, the authors aim to investigate the anti‐diabetic potential of genistein through IC50 value, fluorescence quenching and inhibition kinetics. Genistein was found to exhibit an inhibition activity on α‐glucosidase with an IC50 value of 7.79 ± 0.36 µm. Analysis of fluorescence spectra indicated that genistein quenched enzyme emission through a static mechanism with a bimolecular quenching constant, kq = 4.04 × 1013 m−1 s−1. In addition, it was found that genistein was bound to α‐glucosidase with a high affinity of binding constant, Ka = 3.38 × 105 m−1 and a 1:1 stoichiometric ratio (n = 1.06). In order to suggest a possible contact involved, 8‐anilino‐1‐naphthalenesulfonic acid (ANS) was added as an extrinsic fluorescence probe to enzyme solution and analyzed fluorescence spectra of the α‐glucosidase‐ANS complexes. When treated with genistein, fluorescence intensities of the complexes were reduced remarkably, indicating that genistein interacts with the enzyme via a hydrophobic domain. Finally, the inhibition constant and inhibition mode were studied by inhibition kinetics. The results revealed that genistein bound easily to α‐glucosidase with a Ki value of 25.61 × 10−6 m through a non‐competitive type.