Changes of porcine pancreas α-amylase in activity and secondary conformations under inhibition of tea polyphenols.

To investigate two-sided functions of tea polyphenols ( TP) in antinutrition and energy balance modulation, TP were extracted from Chinese green tea and used to complex porcine pancreas α-amylase ( PPA). Changes of PPA in activity and secondary conformations were analysed. Porcine pancreas α-amylase was found sensitive to TP treatment. Tea polyphenols exhibited IC50 at 0.41 mg mL−1 against PPA and maximum inhibitory rate (98.17%) at 3.0 mg mL−1. Tea polyphenols inhibition was concluded as noncompetitive pattern based on its unchanged Km value (0.98 mg mL−1) for soluble starch substrate. Tea polyphenols inhibition arose from pH 1.5 to 10.14, covering gastric and intestinal environments inside body. Circular dichroism spectra analysis revealed regular changes of PPA in secondary conformations (increased proportions of α-helix and β-sheet) prior to its inactivation at low TP concentrations. Tea polyphenols-inhibited PPA had distinct double-negative peaks at 204 nm and 208 nm. Porcine pancreas α-amylase was inactivated by TP in ways of complexation and modification of secondary conformations. [ABSTRACT FROM AUTHOR]