Regio and enantioselective reduction of t-butyl 6-chloro-3,5-dioxohexanoate with baker’s yeast

Research Progress on the Enhancement of Immobilized Enzyme Catalytic Performance and Its Application in the Synthesis of Vitamin E Succinate

Vitamin E succinate is a more mature vitamin E derivative, and its chemical stability and many effects have been improved compared with vitamin E, which can not only make up for the shortcomings of vitamin E application but also broaden the application field of vitamin E. At present, in developed countries such as Europe, America, and Japan, vitamin E succinate is widely used in health foods, and due to its good water solubility and stability, the vitamin E added to most nutritional supplements (tablets and hard capsules) is vitamin E succinate. At the same time, vitamin E succinate used in the food and pharmaceutical industries is mainly catalyzed by enzymatic catalysis. In this paper, Candida rugosa lipase (CRL) was studied. Chemical modification and immobilization were used to improve the enzymatic properties of CRL, and immobilized lipase with high stability and high activity was obtained. It was applied to the enzymatic synthesis of vitamin E succinate, and the reaction conditions were optimized to improve the yield and reduce the production cost. The review covered the research progress of the methods for enhancing the catalytic performance of immobilized enzymes and discussed its application in the synthesis of vitamin E succinate, providing new ideas and technical support for the catalytic performance enhancement of immobilized enzymes and its application in the synthesis of vitamin E succinate and promoting the production and application of vitamin E succinate.

Chemoenzymatic synthesis of statine side chain building blocks and application in the total synthesis of the cholesterol-lowering compound solistatin

The synthesis and enzymatic reduction of several 6-substituted dioxohexanoates are presented. Two-step syntheses of tert-butyl 6-bromo-3,5-dioxohexanoate and the corresponding 6-hydroxy compound have been achieved in 89% and 59% yield, respectively. Regio- and enantioselective reduction of these diketones and of the 6-chloro derivative with alcohol dehydrogenase from Lactobacillus brevis (LBADH) gave the (5S)-5-hydroxy-3-oxo products with enantiomeric excesses of 91%, 98.4%, and >99.5%, respectively. Chain elongation of the reduction products by one carbon via cyanide addition, and by more than one carbon by Julia-Kocienski olefination, gave access to well-established statine side-chain building blocks. Application in the synthesis of the cholesterol-lowering natural compound solistatin is given.

Kinetic mechanism of an aldehyde reductase of Saccharomyces cerevisiae that relieves toxicity of furfural and 5-hydroxymethylfurfural

An effective means of relieving the toxicity of furan aldehydes, furfural (FFA) and 5-hydroxymethylfurfural (HMF), on fermenting organisms is essential for achieving efficient fermentation of lignocellulosic biomass to ethanol and other products. Ari1p, an aldehyde reductase from Saccharomyces cerevisiae, has been shown to mitigate the toxicity of FFA and HMF by catalyzing the NADPH-dependent conversion to corresponding alcohols, furfuryl alcohol (FFOH) and 5-hydroxymethylfurfuryl alcohol (HMFOH). At pH 7.0 and 25°C, purified Ari1p catalyzes the NADPH-dependent reduction of substrates with the following values (k(cat) (s(-1)), k(cat)/K(m) (s(-1)mM(-1)), K(m) (mM)): FFA (23.3, 1.82, 12.8), HMF (4.08, 0.173, 23.6), and dl-glyceraldehyde (2.40, 0.0650, 37.0). When acting on HMF and dl-glyceraldehyde, the enzyme operates through an equilibrium ordered kinetic mechanism. In the physiological direction of the reaction, NADPH binds first and NADP(+) dissociates from the enzyme last, demonstrated by k(cat) of HMF and dl-glyceraldehyde that are independent of [NADPH] and (K(ia)(NADPH)/k(cat)) that extrapolate to zero at saturating HMF or dl-glyceraldehyde concentration. Microscopic kinetic parameters were determined for the HMF reaction (HMF+NADPH↔HMFOH+NADP(+)), by applying steady-state, presteady-state, kinetic isotope effects, and dynamic modeling methods. Release of products, HMFOH and NADP(+), is 84% rate limiting to k(cat) in the forward direction. Equilibrium constants, [NADP(+)][FFOH]/[NADPH][FFA][H(+)]=5600×10(7)M(-1) and [NADP(+)][HMFOH]/[NADPH][HMF][H(+)]=4200×10(7)M(-1), favor the physiological direction mirrored by the slowness of hydride transfer in the non-physiological direction, NADP(+)-dependent oxidation of alcohols (k(cat) (s(-1)), k(cat)/K(m) (s(-1)mM(-1)), K(m) (mM)): FFOH (0.221, 0.00158, 140) and HMFOH (0.0105, 0.000104, 101).

Stereochemistry of furfural reduction by a Saccharomyces cerevisiae aldehyde reductase that contributes to in situ furfural detoxification

Ari1p from Saccharomyces cerevisiae, recently identified as an intermediate-subclass short-chain dehydrogenase/reductase, contributes in situ to the detoxification of furfural. Furfural inhibits efficient ethanol production by yeast, particularly when the carbon source is acid-treated lignocellulose, which contains furfural at a relatively high concentration. NADPH is Ari1p's best known hydride donor. Here we report the stereochemistry of the hydride transfer step, determined by using (4R)-[4-(2)H]NADPD and (4S)-[4-(2)H]NADPD and unlabeled furfural in Ari1p-catalyzed reactions and following the deuterium atom into products 2-furanmethanol or NADP(+). Analysis of the products demonstrates unambiguously that Ari1p directs hydride transfer from the si face of NADPH to the re face of furfural. The singular orientation of substrates enables construction of a model of the Michaelis complex in the Ari1p active site. The model reveals hydrophobic residues near the furfural binding site that, upon mutation, may increase specificity for furfural and enhance enzyme performance. Using (4S)-[4-(2)H]NADPD and NADPH as substrates, primary deuterium kinetic isotope effects of 2.2 and 2.5 were determined for the steady-state parameters k(cat)(NADPH) and k(cat)/K(m)(NADPH), respectively, indicating that hydride transfer is partially rate limiting to catalysis.

Chemical diversity through biotransformations

Diversity constitutes an intrinsic property of biosynthesis. This inherent property can be exploited and successfully applied in organic synthesis. Recent advances have been made in many areas, including the use of multifunctional enzymes and catalytic promiscuity, the synthesis of diverse products from a single substrate, the use of different biotransformations to make one product, and the use of in vivo biotransformations.