Table 2. Nicotinamide Ring Puckering in Complexes of Horse Liver ADH^a.

ligands	PDB entries	α-C4 (deg)	α-N1 (deg)	twist (Å)
NADH, H2Ob	4XD2	16.0 ± 1.6	12.6 ± 2.2	–0.26 ± 0.03
NADH, MHFc	1P1R, 5VN1	18.1 ± 4.2	11.2 ± 2.3	–0.04 ± 0.12
NADH, BNFd	5VL0	12.5 ± 3.9	13.1 ± 3.2	0.07 ± 0.07
NADH, variouse	1HET, 2JHG	12.3 ± 2.5	11.0 ± 4.5	–0.31 ± 0.19
NAD+, FALCf	4DXH, 4DWV	4.9 ± 2.3	5.8 ± 2.1	0.06 ± 0.03

^aThe structures were refined with relaxed or no restraints on the nicotinamide ring. Ring puckering geometry is defined as follows: α-C4, angle between the C3–C4–C5 and C2–C3–C6 planes; α-N1, angle between the C2–N1–C6 and C2–C3–C6 planes; twist, distortion of the boat conformation, defined as the distance between C5 and the C2–C3–C6 plane.²²

^bWeighted average from two subunits as calculated with SHELXL-2013 with no restraints on the nicotinamide ring.

^cAverage of eight subunits of the enzyme complexed with NADH and N-1-methylhexylformamide, an aldehyde analogue and potent inhibitor,¹¹ calculated with SHELXL-2013 after refinement with REFMAC.

^dAverage of four subunits of the enzyme complexed with NADH and N-benzylformamide calculated with SHELXL-2013 after refinement with REFMAC.

^eAverage of eight subunits from four structures of wild-type ADH with Zn(II) or Cd(II) at the active sites, complexed with NADH and other ligands, including water, methylpentanediol, dimethyl sulfoxide, or isobutyramide (PDB entries 1HEU, 2JHF, 1HET, and 2JHG).^22,23

^fWeighted average of four subunits of the enzyme complexed with NAD⁺ and 2,3,4,5,6-pentafluorobenzyl alcohol or 2,2,2-trifluoroethanol calculated with SHELXL-2013 with no restraints on the nicotinamide ring.⁶²