Fig. 27.20 Crystallographically determined binding geometry of sorbinil 27.50 to aldose reductase. The inhibitor’s hydantoin group binds above the nicotinamide ring of the cofactor to Tyr48, Trp79, and His110. The specificity pocket remains closed during this binding. This pocket can be opened by twisting the side chain of Phe122 and Leu300 out of space.