Abstract:

To investigate the inhibition mechanism of epigallocatechin gallate (EGCG) on glucoamylase and its effect on glucoamylase structure during the digestion process, the methods including inhibition kinetics, fluorescence intensity, surface hydrophobicity analysis and molecular docking were comprehensively adopted. It was shown that EGCG exhibited mixed competitive inhibition on glucoamylase with competitive inhibition as the main factor. As the mass concentration of EGCG increased, the fluorescence intensity of glucoamylase at 425 nm gradually decreased, and the linear relationship of the Stern-Volmer curve of fluorescence quenching was good, and the fluorescence quenching mode belonged to static quenching. With the increase in EGCG mass concentration, the surface hydrophobic interaction of glucoamylase gradually decreased. The molecular docking revealed that the EGCG was bound to amino acids on the non-catalytic site of glucoamylase. It was concluded that the binding of EGCG to the non-catalytic site of glucoamylase affected the binding of the catalytic site and substrate, changed the structure of glucoamylase, affected the hydrophobic interaction of glucoamylase, thus reduced the catalytic efficiency of glucoamylase. These findings provided theoretical basis for the understanding of the interaction mechanism between EGCG and glucoamylase.

Key words: epigallocatechin gallate, glucoamylase, inhibition kinetics