Synthesis with good enantiomeric excess of both enantiomers of alpha-ketols and acetolactates by two thiamin diphosphate-dependent decarboxylases

TitleSynthesis with good enantiomeric excess of both enantiomers of alpha-ketols and acetolactates by two thiamin diphosphate-dependent decarboxylases
Publication TypeJournal Article
Year of Publication2006
AuthorsBaykal, A, Chakraborty S, Dodoo A, Jordan F
JournalBioorganic Chemistry
Volume34
Pagination380-393
Date PublishedDec
Type of ArticleArticle
ISBN Number0045-2068
Accession Numberhttp://apps.isiknowledge.com/InboundService.do?Func=Frame&product=WOS&action=retrieve&SrcApp=EndNote&Init=Yes&SrcAuth=ResearchSoft&mode=FullRecord&UT=000242677800006
Keywordsacetoin, acetolactate, ACID-BASE GROUPS, ACYLOINS, beta-hydroxypyruvate, carboligase side reactions, CATALYSIS, circular dichroism, enantiomeric excess, enzymatic chiral, ENZYMATIC-REACTIONS, ENZYMES, Escherichia coli, ESCHERICHIA-COLI, INTERMEDIATE, pyruvate dehydrogenase E1 subunit, synthesis, TAUTOMERIC FORM, THIAMIN DIPHOSPHATE, YEAST PYRUVATE DECARBOXYLASE, ZYMOMONAS-MOBILIS
Abstract

In addition to the decarboxylation of 2-oxo acids, thiamin diphosphate (ThDP)-dependent decarboxylases/dehydrogenases can also carry out so-called carboligation reactions, where the central ThDP-bound enamine intermediate reacts with electrophilic substrates. For example, the enzyme yeast pyruvate decarboxylase (YPDC, from Saccharomyces cerevisiae) or the El subunit of the Escherichia coli pyruvate dehydrogenase complex (PDHc-E1) can produce acetoin and acetolactate, resulting from the reaction of the central thiamin diphosphate-bound enamine with acetaldehyde and pyruvate, respectively. Earlier, we had shown that some active center variants indeed prefer such a carboligase pathway to the usual one [Sergienko, Jordan, Biochemistry 40 (2001) 7369-7381; Nemeria et al., J. Biol. Chem. 280 (2005) 21,473-21,482]. Herein is reported detailed analysis of the stereoselectivity for forming the carboligase products acetoin, acetolactate, and phenylacetylcarbinol by the E477Q and D28A YPDC, and the E636A and E636Q PDHc-E1 active-center variants. Both pyruvate and beta-hydroxypyruvate were used as substrates and the enantiomeric excess was analyzed by a combination of NMR, circular dichroism and chiral-column gas chromatographic methods. Remarkably, the two enzymes produced a high enantiomeric excess of the opposite enantiomer of both acetoin-derived and acetolactate-derived products, strongly suggesting that the facial selectivity for the electrophile in the carboligation is different in the two enzymes. The different stereoselectivities exhibited by the two enzymes could be utilized in the chiral synthesis of important intermediates. (c) 2006 Elsevier Inc. All rights reserved.

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Alternate JournalBioorganic Chem.