Key points are not available for this paper at this time.
Alignment of all known, diverse members of the aldehyde dehydrogenase (ALDH) extended family revealed only two strictly conserved, nonglycine residues, a glutamate and a phenylalanine residue. Both occur in one of the highly conserved 'motif' segments and both occupy strategic locations in the tertiary structure at the bottom of the catalytic funnel. In class 3 ALDH, these are Glu333 and Phe335. In addition, Asp247, which is not highly conserved but is characteristic of class 3 ALDHs, hydrogen bonds the main chain between Glu333 and Phe335. These three residues were mutated conservatively. Michaelis constants determined for both NAD/propanal and NADP/benzaldehyde substrate pairs show all three residues to be crucial to effective catalysis, and suggest that the hydrogen bond to Asp247 is a key element in maintaining precise geometry of key elements at the active site.
Hempel et al. (2001) studied this question.