Study of conformation and thermodynamics of α-amylase interaction with ethylene in vitro

In this article, the conformation and thermodynamics of α-amylase interaction with ethylene in vitro were investigated. The ultraviolet (UV) absorption showed a strong peak of α-amylase treated with 6.04, 29.32 and 262.11μmolL(-1) ethylene appears at ~222nm and a weak peak at 278nm blue-shifted 1nm. Circular dichroism (CD) spectra indicated that the conformations of α-amylase treated with 29.32 and 262.11μmolL(-1) ethylene were obviously changed in which α-helix content were decreased by 20 and 31% respectively, and β-sheet, β-turn and random coil contents were increased by contrast. Fluorescence spectra suggested that the peak intensities of α-amylase at 342nm were obviously increased with the ethylene increase from 6.04 to 525.75μmolL(-1) and more than control group. The binding constants K between ethylene and α-amylase were 3.318×10(6), 4.407×10(6) and 5.125×10(6)Lmol(-1) at 288, 298 and 308K, respectively. And the calculated values of ΔH(0) and ΔS(0) are positive, which suggests that the interaction between ethylene and α-amylase is an endothermic reaction. The negative ΔG(0) values implied that the direct effect of ethylene on α-amylase conformation was spontaneous. The possible reason is that ethylene molecules were easily embedded into the interior of α-amylase in term of the hydrophobic force between α-amylase and ethylene, causing the conformation and thermodynamics changes of α-amylase.