Aldehyde reductase EC 1.1.1.2 and similar enzymes

Various enzymes that transfer hydrogen from NADPH to a carbonyl compound have broad substrate specificity and, if acetaldehyde will serve, are classifiable as EC 1.1.1.2. 

Aldehyde reductase from human liver catalyses attack by the 4-pro-R hydrogen on the Re face of the carbonyl [135]. 4-Nitrobenzaldehyde and 3,4-dihydroxyphenylglycolaldehyde are good substrates [135,136]. This enzyme is monomeric with molecular weight 36000 [137]. Pig kidney [138] and pig liver [139] also contain a monomeric aldehyde reductase that catalyses Re attack by the 4-pro-R hydrogen, and has molecular weight around 35000. Several other tissues and species contain closely similar enzymes [140-142]. 

There is, however, a further group of NADPH-dependent carbonyl reductases that transfer the 4-pro-S hydrogen [143]. These include human brain aldehyde reductase I [144], liver xenobiotic ketone reductase [145] and prostaglandin 9-ketoreductase [146], all monomeric proteins with molecular weights in the range of 30000-400000. 

The synthesis of lignin from phenylalanine in plants involves two successive (and 

The enzyme (studied in soybean, Glycine max L.) has molecular weight 38000 [148], and transfers the 4-pro-S hydrogen [149]. 

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