Reductive enzymes aldo/keto reductases

Dehydrogenases often act primarily to reduce a carbonyl compmmd rather than to dehydrogenate an alcohol. These enzymes may still be called dehydrogenases. For example, in the lactic acid fermentation lactate is formed by reduction of pyruvate but we still call the enzyme lactate dehydrogenase. In our bodies this enzyme functions in both directions. However, some enzymes that act mainly in the direction of reduction are called reductases. An example is aldose leductase, a member of a family of aldo-keto reductases which have (a / P)g-barrel structures. ... 

Diverse soluble enzymes, called aldo-keto reductases. cany out bioreduction of aldehydes and ketones. They are found in the liver and other tissues (e.g.. kidney). As a general class, these soluble en7.ynie.s have similar physi-ochemical properties and broad substrate specificities and require NADW as a cofactor. Oxidoreductase enzymes that catty out both oxidation and reduction reactions also can reduce aldehydes and ketones. " For example. Ihe important liver alcohol dehydrogenase is an NAD -dependent oxido-icductase that oxidizes ethanol and other aliphatic alcohols to aldehydes and ketones. In the presence of NADH or... 

Discrete plant KRs have been identified that interact with CHS for the biosynthesis of 6 -deoxychalcone (20) (Fig. 3D) [133, 136-139]. Interestingly, the plant KR has no similarity with those that catalyze the reduction of the poly- -ketone intermediates in polyketide or fatty acid biosynthesis [49, 50, 81-84]. Instead it is similar to various aldo/keto-reductases, mostly from carbohydrate metabolism [139-141], and contains a leucine zipper motif known to be involved in protein-protein interaction [142]. Plant 0-methyltransferases are well known [143], but enzymes for C-methylation have not been described. The... 

Aldose reductase (ALR2 EC 1.1.1.21) is an 36 kDa enzyme that catalyzes the reduction of a wide range of carbonyl-containing compounds to their corresponding alcohols. It is a member of an extensive aldo-keto oxidoreductase enzyme family, a collection of structurally similar proteins expressed in both animals and plants. Most members of the enzyme family possess similarities in molecular mass, pH optimum, coenzyme dependence, and demonstrate overlapping specificity for many substrates and inhibitors. 

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