Aldehyde dehydrogenase diol oxidation

Although alcohol dehydrogenases (ADH) also catalyze the oxidation of aldehydes to the corresponding acids, the rate of this reaction is significantly lower. The systems that combine ADH and aldehyde dehydrogenases (EC 1.2.1.5) (AldDH) are much more efficient. For example, HLAD catalyzes the enantioselective oxidation of a number of racemic 1,2-diols to L-a-hydroxy aldehydes which are further converted to L-a-hydroxy acids by AldDH (166). 

Alcohol dehydrogenases also oxidize aldehydes, probably most often as the geminal diol forms, according to Eq. 15-8. No ATP is formed. The same enzymes can catalyze the dismutation of aldehydes, with equal numbers of aldehyde molecules going to carboxylic acid and to the alcohol.96-98... 

C-H Wong, JR Matos. Enantioselective oxidation of 1,2-diols to L-a-hydroxy acids using co-immobilized alcohol and aldehyde dehydrogenases as catalysts. J Org Chem 50 1992-1994, 1985. 

The use of enzymes for the enantioselective oxidation of prochiral (or racemic) diols has proved to be of significant synthetic interest. A range of simple racemic 1,2-diols proved to be good substrates for a system involving coimmobilized horse liver alcohol dehydrogenase (HLADH) and aldehyde dehydrogenase (AldDH) with NAD cofactor recycling. This produced enantiomerically pure a-hydroxycarbox-ylic acids (Scheme 12). 

Wong and Matos (1985) reported a stereospecific oxidation of 1,2--diols to a-hydroxy carboxylic acids via a-hydroxy aldehydes.. The trick employed here is to coimmobilize HLADH and aldehyde dehydrogenase (AldDH) into polyacrylamide. The former enzyme oxidizes the diol to the corresponding a-hydroxy aldehyde, which is further oxidized to the a-hydroxy carboxylic acid by the latter enzyme (Scheme 34). After 40 % conversion of the substrates, enantiomer... 

Wong CH, Matos JR (1985) Enantioselective oxidation of 1,2-diols to L-a-hydroxy acids using coimmobilized alcohol and aldehyde dehydrogenase as catalysts. J Org Chem 50 1992-1994 Yasui S, Nakamura K, Ohno A, Oka S (1982) Reduction by a model of NAD(P)H. 36. First and direct evidence for the multi-step mechanism. Bull Chem Soc Jpn 55 196-199 Yasui S, Nakamura K, Ohno A (1983) Reduction by a model of NAD(P)H. 42. Direct evidence for one electron transfer mechanism in the reduction of arenediazonium salts. Tetrahedron Lett 24 3331-3334 Yasui S, Nakamura K, Ohno A (1984) Reduction by a model of NAD(P)H. 45. Mechanism for the dediazonation of arenediazonium salts initiated by one-electron transfer from an NAD(P)H-model. J Org Chem 49 878-882... 

The oxidation of aldehydes to carboxylic acids has been most extensively investigated with horse liver alcohol dehydrogenases (65-67, 69, 73). There are two distinct reactions the direct oxidation of aldehydes as their hydrated gem-diol form [reaction (9)] and the oxidation of hemiacetals to esters [oxidative esterification, reaction (10)]. 

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