The aldo-keto reductase family includes a number of related monomeric
NADPH-dependent oxidoreductases, such as aldehyde reductase, aldose
reductase, prostaglandin F synthase, xylose reductase, rho crystallin, and
many others . All possess a similar structure, with a beta-alpha-beta fold
characteristic of nucleotide binding proteins .
The fold comprises a parallel beta-8/alpha-8-barrel, which contains a
novel NADP-binding motif. The binding site is located in a large,
deep, elliptical pocket in the C-terminal end of the beta sheet, the
substrate being bound in an extended conformation. The hydrophobic
nature of the pocket favours aromatic and apolar substrates over highly
polar ones .
Binding of the NADPH coenzyme causes a massive
conformational change, reorienting a loop, effectively locking the
coenzyme in place. This binding is more similar to FAD- than to
NAD(P)-binding oxidoreductases .
Some proteins of this entry contain a K+ ion channel beta chain regulatory domain; these are reported to have oxidoreductase activity .