Isotope Probing of the UDP-Apiose/UDP-Xylose Synthase Reaction: Evidence of a Mechanism via a Coupled Oxidation and Aldol Cleavage

Thomas Eixelsberger, Doroteja Horvat, Alexander Gutmann, Hansjörg Weber, Bernd Nidetzky

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The C-branched sugar d-apiose (Api) is essential for plant cell-wall development. An enzyme-catalyzed decarboxylation/pyranoside ring-contraction reaction leads from UDP-α-d-glucuronic acid (UDP-GlcA) to the Api precursor UDPa-d-apiose (UDP-Api). We examined the mechanism of UDPApi/UDP-α-d-xylose synthase (UAXS) with site-selectively 2H-labeled and deoxygenated substrates. The analogue UDP-2-deoxy-GlcA, which prevents C-2/C-3 aldol cleavage as the plausible initiating step of pyranoside-to-furanoside conversion, did not give the corresponding Api product. Kinetic isotope effects (KIEs) support an UAXS mechanism in which substrate oxidation by enzyme-NAD+ and retro-aldol sugar ring-opening occur coupled in a single rate-limiting step leading to decarboxylation. Rearrangement and ring-contracting aldol addition in an open-chain intermediate then give the UDP-Api aldehyde, which is intercepted via reduction by enzyme-NADH

LanguageEnglish
Pages2503 –2507
JournalAngewandte Chemie (Weinheim) / International edition in English
Volume56
DOIs
StatusPublished - 2017

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Xylose
Uridine Diphosphate
Isotopes
Enzymes
Sugars
Oxidation
NAD
Catalyst supports
Glucuronic Acid
Kinetics
Acids
Substrates
UDP-apiose
UDPglucuronate decarboxylase
3-hydroxybutanal

Fields of Expertise

  • Human- & Biotechnology

Cite this

Isotope Probing of the UDP-Apiose/UDP-Xylose Synthase Reaction: Evidence of a Mechanism via a Coupled Oxidation and Aldol Cleavage. / Eixelsberger, Thomas; Horvat, Doroteja; Gutmann, Alexander; Weber, Hansjörg; Nidetzky, Bernd.

In: Angewandte Chemie (Weinheim) / International edition in English, Vol. 56, 2017, p. 2503 –2507.

Research output: Contribution to journalArticleResearchpeer-review

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abstract = "The C-branched sugar d-apiose (Api) is essential for plant cell-wall development. An enzyme-catalyzed decarboxylation/pyranoside ring-contraction reaction leads from UDP-α-d-glucuronic acid (UDP-GlcA) to the Api precursor UDPa-d-apiose (UDP-Api). We examined the mechanism of UDPApi/UDP-α-d-xylose synthase (UAXS) with site-selectively 2H-labeled and deoxygenated substrates. The analogue UDP-2-deoxy-GlcA, which prevents C-2/C-3 aldol cleavage as the plausible initiating step of pyranoside-to-furanoside conversion, did not give the corresponding Api product. Kinetic isotope effects (KIEs) support an UAXS mechanism in which substrate oxidation by enzyme-NAD+ and retro-aldol sugar ring-opening occur coupled in a single rate-limiting step leading to decarboxylation. Rearrangement and ring-contracting aldol addition in an open-chain intermediate then give the UDP-Api aldehyde, which is intercepted via reduction by enzyme-NADH",
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