Biocatalytic production of alpha-hydroxy ketones and vicinal diols by yeast and human aldo-keto reductases
ABSTRACT The α-hydroxy ketones are used as building blocks for compounds of pharmaceutical interest (such as antidepressants, HIV-protease inhibitors and antitumorals). They can be obtained by the action of enzymes or whole cells on selected substrates, such as diketones. We have studied the enantiospecificities of several fungal (AKR3C1, AKR5F and AKR5G) and human (AKR1B1 and AKR1B10) aldo-keto reductases in the production of α-hydroxy ketones and diols from vicinal diketones. The reactions have been carried out with pure enzymes and with an NADPH-regenerating system consisting of glucose-6-phosphate and glucose-6-phosphate dehydrogenase. To ascertain the regio and stereoselectivity of the reduction reactions catalyzed by the AKRs, we have separated and characterized the reaction products by means of a gas chromatograph equipped with a chiral column and coupled to a mass spectrometer as a detector. According to the regioselectivity and stereoselectivity, the AKRs studied can be divided in two groups: one of them showed preference for the reduction of the proximal keto group, resulting in the S-enantiomer of the corresponding α-hydroxy ketones. The other group favored the reduction of the distal keto group and yielded the corresponding R-enantiomer. Three of the AKRs used (AKR1B1, AKR1B10 and AKR3C1) could produce 2,3-butanediol from acetoin. We have explored the structure/function relationships in the reactivity between several yeast and human AKRs and various diketones and acetoin. In addition, we have demonstrated the utility of these AKRs in the synthesis of selected α-hydroxy ketones and diols.
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ABSTRACT: Acetoin (3-hydroxy-2-butanone) is an important flavour compound and is applied in cosmetics, pharmacy and chemical synthesis. In contrast to chemical syntheses or fermentations an enzymatic route facilitates enantioselective acetoin production. The discovery of a (S)-selective alcohol dehydrogenase enables a novel production process of (R)-acetoin from meso-2,3-butanediol. It was shown that the regeneration of oxidised nicotinamide adenine dinucleotide is a key point in preparative application of dehydrogenases for the oxidative route. An electrochemical regeneration system was successful combined with the ADH catalysed reaction. Up to 48 mM (R)-acetoin was produced in the reaction system while productivities up to 2 mM h(-1) were reached. The possibility to apply an electrochemical system in a semi-preparative synthesis will stimulate further research of electroenzymatic processes with oxidoreductases.Journal of Molecular Catalysis B Enzymatic 05/2014; 103. DOI:10.1016/j.molcatb.2013.08.016 · 2.75 Impact Factor
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ABSTRACT: Human aldo-keto reductase 1B15 (AKR1B15) is a newly discovered enzyme which shares 92% amino acid sequence identity with AKR1B10. While AKR1B10 is a well characterized enzyme with high retinaldehyde reductase activity, involved in the development of several cancer types, the enzymatic activity and physiological role of AKR1B15 are still poorly known. Here, the purified recombinant enzyme has been subjected to substrate specificity characterization, kinetic analysis and inhibitor screening, combined with structural modeling. AKR1B15 is active towards a variety of carbonyl substrates, including retinoids, with lower k <sub>cat</sub> and K<sub>m</sub> values than AKR1B10. In contrast to AKR1B10, which strongly prefers all- trans -retinaldehyde, AKR1B15 exhibits superior catalytic efficiency with 9- cis -retinaldehyde, the best substrate found for this enzyme. With ketone and dicarbonyl substrates, AKR1B15 also shows higher catalytic activity than AKR1B10. SPLoS ONE 07/2015; 10(7-7):e0134506. DOI:10.1371/journal.pone.0134506 · 3.23 Impact Factor