Binding mechanism of lipase to Ligupurpuroside B extracted from Ku-Ding tea as studied by multi-spectroscopic and molecular docking methods

The interaction of lipase with Ligupurpuroside B was studied by multiple spectroscopic techniques, enzyme activity and molecular modeling under simulative physiological condition. According to Stern-Volmer equation, fluorescence of lipase was quenched by Ligupurpuroside B via a static quenching mechanism because of formation of Ligupurpuroside B-lipase complex. Binding constants, number of binding sites & thermodynamic parameters were evaluated. The values of Delta G degrees (-25.085 kJ mol(-1)), Delta H degrees (-12.14 kJ mol(-1)) and Delta S degrees (+43.45 J mol(-1) K-1) at 298 K indicated that Ligupurpuroside B-lipase interaction is spontaneous and hydrophobic interaction is the main force stabilizing the Ligupurpuroside B-lipase complex. The enzyme activity assay showed that Ligupurpuroside B inhibited lipase activity efficiently. Synchronous fluorescence spectra (SFS) suggested that Ligupurpuroside B is closer to Trp residues than to Tyr residues. All above experimental results were confirmed by molecular docking studies, which further indicated the binding site of Ligupurpuroside B on the surface of lipase, and the amino acid residues of lipase interacting with Ligupurpuroside B. Our present research work gives valuable information on the design of drugs with lipase as a carrier and should be useful for food industries. (C) 2018 Elsevier B.V. All rights reserved.