Secondary-alcohol oxidoreductase

Secondary-alcohol oxidoreductase Polyvinyl alcohol oxidase, PVA oxidase, SAO —... 

Forrest et al. (183) isolated and sequenced a gene from liver encoding an NADPH-dependent carbonyl (i.e., n-oxo-anthracycline) reductase. The enzyme belonged to a class of secondary alcohol oxidoreductases and was related to the Streptomyces sp. strain C5 ketoreductase encoded by arfl (280 renamed in this chapter to doHlJ). Interestingly, Forrest et al. (183) indicated that the liver enzyme also catalyzed reduction of the anthra eye line quinone as well. 

It is well established that oxygen in the presence of platinum (Adams catalyst) can achieve specific oxidation of secondary alcohols by a preferential attack upon hydrogen in an equatorial position (25). Catalytic oxidation of methyl a- and /3-D-galactopyranoside (26), fallowed by catalytic reduction with hydrogen, led to the formation of methyl a- and /3-6-deoxy-D-galactopyranoside (D-fuco-pyranoside) in 15% and 35% yield, respectively. This oxidation-reduction sequence with selective oxidation at carbon 4 as the initial step is structurally closely related to the above described pathway for TDPG-oxidoreductase. 

Capillary gas chromatographic determination of optical purities, investigation of the conversion of potential precursors, and characterization of enzymes catalyzing these reactions were applied to study the biogenesis of chiral volatiles in plants and microorganisms. Major pineapple constituents are present as mixtures of enantiomers. Reductions, chain elongation, and hydration were shown to be involved in the biosynthesis of hydroxy acid esters and lactones. Reduction of methyl ketones and subsequent enantioselective metabolization by Penicillium citrinum were studied as model reactions to rationalize ratios of enantiomers of secondary alcohols in natural systems. The formation of optically pure enantiomers of aliphatic secondary alcohols and hydroxy acid esters using oxidoreductases from baker s yeast was demonstrated. 

The biocatalytic counterpart for this transformation is done by the alcohol dehydrogenases [ADHs, EC 1.1.1.x., also called ketoreductases (KREDs) or carbonyl reductases (CRs)], which are able to perform stereoselective carbonyl reductions or enantioselective alcohol oxidations [5-8]. These enzymes are probably the most employed oxidoreductases and make use of a nicotinamide cofactor such as NADH or NADPH to transfer electrons into and from the target substrate. Depending on their substrate scope, ADHs can be divided into primary alcohol dehydrogenases, preferentially reducing aldehydes, and secondary alcohol dehydrogenases that have... 

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