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. Author manuscript; available in PMC: 2009 Oct 3.

Published in final edited form as: J Mol Biol. 2008 Jul 7;382(2):371–384. doi: 10.1016/j.jmb.2008.06.083

The nicotinamide distortion and ribose conformation favor catalysis. a) The schematic shows the planes of the nicotinamide and flavin (solid black lines). The hypothesized partial boat is shown as a solid red line. Pyramidalization at the nicotinamide N1 places the lone pair on the flavin side where it (i) entropically favors the productive boat conformation to form and (ii) repels the hydride to be transferred (dashed red line). b) The ribose conformation relative to the nicotinamide stabilizes the electron-deficient NADP⁺ ring orbitals via hyperconjugative electron donation from the ribose. The glycosidic C-O bond position parallel to the nicotinamide ring also favors NADP⁺ over NADPH (see Results & Discussion).

The nicotinamide distortion and ribose conformation favor catalysis. a) The schematic shows the planes of the nicotinamide and flavin (solid black lines). The hypothesized partial boat is shown as a solid red line. Pyramidalization at the nicotinamide N1 places the lone pair on the flavin side where it (i) entropically favors the productive boat conformation to form and (ii) repels the hydride to be transferred (dashed red line). b) The ribose conformation relative to the nicotinamide stabilizes the electron-deficient NADP⁺ ring orbitals via hyperconjugative electron donation from the ribose. The glycosidic C-O bond position parallel to the nicotinamide ring also favors NADP⁺ over NADPH (see Results & Discussion).