The binding mechanism between cyclodextrins and pullulanase: A molecular docking, isothermal titration calorimetry, circular dichroism and fluorescence study.

This work investigated the interaction between cyclodextrins and pullulanase to provide insight into the production and application of cyclodextrins. Enzyme activity and kinetic assays showed that α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) inhibited pullulanase in a competitive manner. Circular dichroism spectra and fluorescence spectroscopy suggested the formation of cyclodextrin and pullulanase complexes. According to ITC assays and molecular docking results, compared with α-CD and γ-CD, β-CD had the strongest affinity for pullulanase because of its appropriate cavity geometric dimensions. In addition, cyclodextrins interacted with pullulanase through hydrogen bonds, van der Waals force and hydrophobic interactions, the latter of which were verified as the major driving force. Phenylalanine 476 was the key amino acid residue in pullulanase for cyclodextrin recognition and binding.

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Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.