1.1.1.331	crystal structures of the apo-form and binary/ternary complexes at 1.6, 2.8, and 2.0 A resolution, respectively. The enzyme is a homotetramer, consisting of an alpha/beta single domain monomer containing seven parallel beta-strands flanked by eight alpha-helices on both sides. Its overall monomeric structure shows a conserved Asp47 residue forming a hydrogen bond with both hydroxyl groups of the adenine ribose of NAD(H), and thus specificity toward NAD(H) instead of NADP(H). The highly conserved catalytic triad Ser153, Tyr167, and Lys171 is adjacent to both NAD(H) and substrate molecules, where Tyr167 functions as a general base