 The enzyme encoded by the human ALDH2 gene is a tetrameric enzyme that contains three domains; two dinucleotide-binding domains and a three-stranded beta-sheet domain.The active site of ALDH2 is divided into two halves by the nicotinamide ring of NAD+.Adjacent to the A-side (Pro-R) of the nicotinamide ring is a cluster of three cysteines (Cys301, Cys302 and Cys303) and adjacent to the B-side (Pro-S) are Thr244, Glu268, Glu476 and an ordered water molecule bound to Thr244 and Glu476.