Dehydrogenases chiral compound synthesis

M. R. Kula, U. Kragl, Dehydrogenases in the synthesis of chiral compounds" in R. Patel, Stereoselective Biocatalysis, Marcel Dekker, 2000, 839. 

Hummel, W. (1997) New alcohol dehydrogenases for the synthesis of chiral compounds. Advances in Biochemical Engineering/Biotechnology, 58, 145-184. 

Enzyme reductions of carbonyl groups have important applications in the synthesis of chiral compounds (as described in Chapter 10). Dehydrogenases are enzymes that catalyse, for example, the reduction of carbonyl groups they require co-factors as their co-substrates. Dehydrogenase-catalysed transformations on a practical scale can be performed with purified enzymes or with whole cells, which avoid the use of added expensive co-factors. Bakers yeast is the whole cell system most often used for the reduction of aldehydes and ketones. Biocatalytic activity can also be used to reduce carbon carbon double bonds. Since the enzymes for this reduction are not commercially available, the majority of these experiments were performed with bakers yeast1 41. 

Reductive amination reactions of keto acids are performed with amino acid dehydrogenases. NAD-dependent leucine dehydrogenase from Bacillus sp. is of interest for the synthesis of (S)-fert.-leucine [15-17]]. This chiral compound has found widespread application in asymmetric synthesis and as a building block of biologically active substances. The enzyme can also be used for the chemoenzy-matic preparation of (S)-hydroxy-valine [18] and unnatural hydrophobic bran-ched-chain (S)-amino acids. NAD-dependent L-phenylalanine dehydrogenase from Rhodococcus sp. [19] has been used for the synthesis of L-homophenyl-alanine ((S)-2-Amino-4-phenylbutanoic acid) [9]. These processes with water-soluble substrates and products demonstrate that the use of coenzymes must not... 

The other four chapters of this volume are contributed by heads of department from the Institute of Enzyme Technology at Heinrich Heine University, Diisseldorf, of which Prof. Kula is the director. First of all, Privatdozent Dr. Werner Hummel concerns himself with New Alcohol Dehydrogenases for the Synthesis of Chiral Compounds . Up to just a few years ago, it was believed that due to the cofactor regeneration problem oxidoreductases could not be applied in practice. In his contribution, Dr. Hummel shows that an interesting pathway to chiral alcohols has been opened up by the provision of suffi-... 

In addition to stereoselective metalation, other methods have been applied for the synthesis of enantiomerically pure planar chiral compounds. Many racemic planar chiral amines and acids can be resolved by both classical and chromatographic techniques (see Sect. 4.3.1.1 for references on resolution procedures). Some enzymes have the remarkable ability to differentiate planar chiral compounds. For example, horse liver alcohol dehydrogenase (HLADH) catalyzes the oxidation of achiral ferrocene-1,2-dimethanol by NAD to (S)-2-hydroxymethyl-ferrocenealdehyde with 86% ee (Fig. 4-2la) and the reduction of ferrocene-1,2-dialdehyde by NADH to (I )-2-hydroxymethyl-ferrocenealdehyde with 94% ee (Fig. 4-2lb) [14]. Fermenting baker s yeast also reduces ferrocene-1,2-dialdehyde to (I )-2-hydroxymethyl-ferro-cenealdehyde [17]. HLADH has been used for a kinetic resolution of 2-methyl-ferrocenemethanol, giving 64% ee in the product, (S)-2-methyl-ferrocenealdehyde... 

Fructose 1,6 bisphosphate (FBP) is an allosteric activator of the thermostable l-2-hydroxyacid dehydrogenase from B. stearothermophilus, which might be useful for the asymmetric synthesis of chiral compounds. Since FBP is quite expensive, Allen and Holbrook wished to create an FBP-independent variant1208. Three rounds of shuffling and screening produced a mutant L-2-hydroxyacid dehydrogenase with three amino acid substitutions that is almost as active in the absence of FBP as the wild-type is in its presence. 

Hummel W, Kula M (1989) Dehydrogenases for the synthesis of chiral compounds. Eur J Biochem 184 1-13... 

Hummel, W. New Alcohol Dehydrogenases for the Synthesis of Chiral Compounds. VoL 58, p. 145 Ikeda, M. Amino Acid Production Processes. Vol. 79, p. 1... 

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