W0270

Atomic Resolution Structures of Human Aldose Reductase Holoenzyme Complexed with Fidarestat and Minalrestat. O. El-Kabbani,¹ C. Darmanin,¹ T.R. Schneider,² I. Hazemann,³ M. Oka,⁴ A. Joachimiak,⁵ C. Schulze-Briesse,⁶ T. Tomizaki,⁶ A. Mitschler,³ and A. Podjarny³ ,¹Dept. of Medicinal Chemistry, Victorian College of Pharmacy, Monash Univ. (Parkville Campus), Australia, ²Dept. of Structural Chemistry, Unive. of Göttingen, Göttingen, Germany, ³UPR de Biologie Structurale, IGBMC, CNRS INSERM ULP, Illkirch, France, ⁴Sanwa Kagaku Kenkyusyo Co., Ltd., Nagoya, Japan, ⁵SBC, APS, Argonne, IL, USA, ⁶SLS, PSI, Villigen, Switzerland.

The X-ray structures of human aldose reductase holoenzyme in complex with the inhibitors Fidarestat (SNK-860) and Minalrestat (WAY-509) were determined at atomic resolutions of 0.92 Å and 1.1 Å, respectively. The hydantoin and succinimide moieties of the inhibitors interacted with the conserved anion-binding site located between the nicotinamide ring of the coenzyme and active site residues Tyr48, His110 and Trp111. Minalrestat’s hydrophobic isoquinoline ring was bound in an adjacent pocket lined by residues Trp20, Phe122 and Trp219, with the bromo-fluorobenzyl group inside the 'specificity' pocket. The interactions between Minalrestat’s bromo-fluorobenzyl group and the enzyme include the stacking against the side-chain of Trp111 as well as hydrogen bonding distances with residues Leu300 and Thr113. The carbamoyl group in Fidarestat formed a hydrogen bond with the main-chain nitrogen atom of Leu300. The atomic resolution refinement allowed the positioning of hydrogen atoms and accurate determination of bond lengths of the inhibitors, coenzyme NADP⁺ and active site residue His110. The clear electron density in the active site region indicated the imidazole ring of His110 was protonated at the Nε2 atom position and formed a hydrogen bond with the negatively charged 1'-position nitrogen atom in the hydantoin and succinimide moieties of Fidarestat and Minalrestat, respectively, an observation that may have important implications on drug design.