Wu Shuyun, Lai Minghua, Luo Jiahao, Pan Jingwen, Zhang Li-Ming, Yang Liqun
Department of Polymer and Material Science, School of Chemistry and Chemical Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Guangdong Provincial Key Laboratory for High Performance Polymer-based Composites, Sun Yat-sen University, Xin-gang West Road 135, Guangzhou 510275, China.
Department of Polymer and Material Science, School of Chemistry and Chemical Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Guangdong Provincial Key Laboratory for High Performance Polymer-based Composites, Sun Yat-sen University, Xin-gang West Road 135, Guangzhou 510275, China.
Int J Biol Macromol. 2017 Jan;94(Pt A):669-678. doi: 10.1016/j.ijbiomac.2016.09.036. Epub 2016 Oct 15.
To understand the mechanism responsible for the α-amylase inhibitory activity of tea polysaccharides, the interaction between α-amylase and an acidic branched tea polysaccharide (TPSA) was investigated using fluorescence spectroscopy and resonance light scattering analysis. TPSA, exhibiting inhibitory activity towards α-amylase (the maximum inhibition percentage of 65%), was isolated from green tea (Camellia sinensis) and characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and gas chromatography. Synchronous fluorescence spectroscopy revealed that the binding interaction between the tryptophan residues of α-amylase and TPSA was predominant. Based on the fluorescence quenching effect of tryptophan residues induced by TPSA, the binding constants between α-amylase and TPSA were determined to be 18.6×10, 8.0×10 and 4.6×10 L·mol at 20, 30 and 37°C, respectively. The calculated Gibbs free-energy changes were negative, indicating that the bonding interaction was a spontaneous process. The enthalpy and the entropy changes were -62.13 KJ·mol and -0.0728 KJ·mol·K, suggesting that hydrogen bonding interactions might play a major role in the binding process. The formation of an α-amylase/TPSA complex was evidenced by fluorescence quenching and resonance light scattering analysis, and this complex could be the main contributor to the α-amylase inhibitory activity of TPSA.
