Alcohol dehydrogenases substrate range

This enzyme [EC 1.1.99.8], also known as alcohol dehydrogenase (acceptor), catalyzes the reaction of a primary alcohol with an acceptor to produce an aldehyde and the reduced acceptor. A wide range of primary alcohols (c.g., methanol) can serve as substrates. 

The results of the temperature dependence of the reaction rates of the enantiomers of secondary alcohols with a secondary alcohol dehydrogenase (SADE1) from the thermophilic bacterium Thermoanaerobacter ethanolicus demonstrated a temperature-dependent reversal of stereospecificity (Pham, 1990) (Figure 5.16). At T < 26°C, (S)-2-butanol was a better substrate than (i )-2-butanol on the basis of kCSLt/KM values however, at T> 26°C, (R)-2-butanol was a better substrate than (S)-2-butanol. (S)-2-Pentanol was the preferred substrate at T < 60°C however, the data predict that (i )-2-pentanol would be preferred at T > 70°C. (S)-2-Elexanol was predicted to be the preferred enantiomer only at T > 240°C. Therefore, the concept of isoinversion temperature is as valid for enzyme reactions as for others only the range of catalytically accessible temperatures is smaller. 

Horse liver alcohol dehydrogenase is a well-documented enzyme capable of operating with high stereoselectivity on a broad structural range of alcohol and carbonyl substrates. The present reaction proceeds via the pathway shown below, where NAD and NADH represent the oxidized and reduced forms, respectively, of the nicotinamide adenine dinucleotide coenzyme. 

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). 

Two classes of macromolecules have received special attention 1) horse liver alcohol dehydrogenase, ADH (7), because of its reactivity with a broad range of substrates and... 

Fig. is. Range of substrates for the horse liver and Drosophila alcohol dehydrogenases (from left to right) secondary alcohols, primary alcohols, hemiacetals, and gem-diols. 

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