title: α-Hydroxy-β-keto acid rearrangement-decarboxylation: impact on thiamine diphosphate-dependent enzymatic transformations.
abstract: The thiamine diphosphate (ThDP) dependent MenD catalyzes the reaction of α-ketoglutarate with pyruvate to selectively form 4-hydroxy-5-oxohexanoic acid 2, which seems to be inconsistent with the assumed acyl donor role of the physiological substrate α-KG. In contrast the reaction of α-ketoglutarate with acetaldehyde gives exclusively the expected 5-hydroxy-4-oxo regioisomer 1. These reactions were studied by NMR and CD spectroscopy, which revealed that with pyruvate the observed regioselectivity is due to the rearrangement-decarboxylation of the initially formed α-hydroxy-β-keto acid rather than a donor-acceptor substrate role variation. Further experiments with other ThDP-dependent enzymes, YerE, SucA, and CDH, verified that this degenerate decarboxylation can be linked to the reduced enantioselectivity of acyloins often observed in ThDP-dependent enzymatic transformations.
authors.affiliation: Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstraße 25, 79104 Freiburg, Germany.
authors.forename: Maryam
authors.initials: M
authors.lastname: Beigi
authors.forename: Sabrina
authors.initials: S
authors.lastname: Loschonsky
authors.forename: Patrizia
authors.initials: P
authors.lastname: Lehwald
authors.forename: Volker
authors.initials: V
authors.lastname: Brecht
authors.forename: Susana L A
authors.initials: SL
authors.lastname: Andrade
authors.forename: Finian J
authors.initials: FJ
authors.lastname: Leeper
authors.forename: Werner
authors.initials: W
authors.lastname: Hummel
authors.forename: Michael
authors.initials: M
authors.lastname: Müller
mesh_terms: D055162:Biocatalysis; D003653:Decarboxylation; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000378:metabolism*; D007656:Ketoglutaric Acids / Q000737:chemistry / Q000378:metabolism*; D011771:Pyruvate Oxidase / Q000378:metabolism*; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D007656:Ketoglutaric Acids; C534108:2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexadiene-1-carboxylate synthase, E coli; D011771:Pyruvate Oxidase; D013835:Thiamine Pyrophosphate