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

•Ethylene alters α-amylase secondary structure by UV, CD and fluorescence spectra analysis.•Binding constants K between ethylene and α-amylase were increased with temperature.•Ethylene was easily embedded into the interior of α-amylase macromolecule in vitro.•Negative ΔG0 values show that interaction between ethylene and α-amylase is spontaneous.

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 262.11 μmol L− 1 ethylene appears at ~ 222 nm and a weak peak at 278 nm blue-shifted 1 nm. Circular dichroism (CD) spectra indicated that the conformations of α-amylase treated with 29.32 and 262.11 μmol L− 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 342 nm were obviously increased with the ethylene increase from 6.04 to 525.75 μmol L− 1 and more than control group. The binding constants K between ethylene and α-amylase were 3.318 × 106, 4.407 × 106 and 5.125 × 106 L mol− 1 at 288, 298 and 308 K, respectively. And the calculated values of ΔH0 and ΔS0 are positive, which suggests that the interaction between ethylene and α-amylase is an endothermic reaction. The negative ΔG0 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.

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