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The inhibition of α-glucosidase is used as a key clinical approach to treat type 2 diabetes mellitus and thus, we assessed the inhibitory effect of α-ketoglutaric acid (AKG) on α-glucosidase with both an enzyme kinetic assay and computational simulations. AKG bound to the active site and interacted with several key residues, including ASP68, PHE157, PHE177, PHE311, ARG312, TYR313, ASN412, ILE434 and ARG439, as detected by protein-ligand docking and molecular dynamics simulations. Subsequently, we confirmed the action of AKG on α-glucosidase as mixed-type inhibition with reversible and rapid binding. The relevant kinetic parameter IC 50 was measured (IC 50 = 1.738 ± 0.041 mM), and the dissociation constant was determined ( K i Slope = 0.46 ± 0.04 mM). Regarding the relationship between structure and activity, a high AKG concentration induced the slight modulation of the shape of the active site, as monitored by hydrophobic exposure. This tertiary conformational change was linked to AKG inhibition and mostly involved regional changes in the active site. Our study provides insight into the functional role of AKG due to its structural property of a hydroxyphenyl ring that interacts with the active site. We suggest that similar hydroxyphenyl ring-containing compounds targeting key residues in the active site might be potential α-glucosidase inhibitors. AbbreviationsAKGalpha-ketoglutaric acidpNPG4-nitrophenyl-α-d-glucopyranosideANS1-anilinonaphthalene-8-sulfonateMDmolecular dynamics.Communicated by Ramaswamy H. Sarma.

Inhibition of α-glucosidase is directly associated with treatment of type 2 diabetes. In this regard, we conducted enzyme kinetics integrated with computational docking simulation to assess the inhibitory effect of raspberry ketone (RK) on α-glucosidase. RK bound to the active site of α-glucosidase and interacted with several key residues such as ASP68, TYR71, HIS111, PHE157, PHE158, PHE177, GLN181, ASP214, THR215, ASP349, ASP408, and ARG439, as detected by protein-ligand docking simulation. Subsequently, we confirmed the action of RK on α-glucosidase as the non-competitive type of inhibition in a reversible and rapidly binding manner. The relevant kinetic parameters were IC 50 =6.17±0.46mM and K i =7.939±0.211mM. Regarding the structure-activity relationship, the higher concentration of RK induced slight modulation of the shape of the active site as monitored by hydrophobic exposure. The tertiary conformational change was linked to RK inhibition, and mostly involved regional changes of the active site. Our study provides insight into the functional role of RK due to its structural property of a hydroxyphenyl ring that interacts with the active site of α-glucosidase. We suggest that similar hydroxyphenyl ring compounds targeting the key residues of the active site might be potential α-glucosidase inhibitors., (Copyright © 2018. Published by Elsevier B.V.)