New insights into EGCG retards the digestion of wheat starch by α-amylase in ternary system: Comparison with binary systems.

This study was to investigate the mechanism of the action of epigallocatechin gallate (EGCG) on α-amylase in the ternary simulated system and explore the changes in enzyme structure during the digestion process. Enzymatic kinetics, fluorescence spectroscopy, surface hydrophobicity, fluorescence microscopy, and molecular docking were used to compare (in the presence and absence of EGCG) the structural changes of α-amylase and α-amylase-starch complex, as well as the binding characteristics among EGCG and the α-amylase and starch. The results showed that EGCG had a significant inhibitory effect on α-amylase, and it exhibited a coexistence of competitive and anti-competition inhibition type, and predominantly competitive inhibition. In the ternary and binary systems, the inhibitory mechanisms of EGCG on α-amylase were distinct. In the ternary system, EGCG preferably bound to α-amylase to form α-amylase-EGCG binary complexes rather than α-amylase-starch-EGCG ternary complexes, and altered the structure of α-amylase, leading to unfolding of the enzyme's secondary structure and exposing more non-catalytic site aromatic amino acids.