Real-time NMR monitoring of intermediates and labile products of the bifunctional enzyme UDP-apiose/UDP-xylose synthase.
نویسندگان
چکیده
The conversion of UDP-alpha-d-glucuronic acid to UDP-alpha-d-xylose and UDP-alpha-d-apiose by a bifunctional potato enzyme UDP-apiose/UDP-xylose synthase was studied using real-time nuclear magnetic resonance (NMR) spectroscopy. UDP-alpha-d-glucuronic acid is converted via the intermediate uridine 5'-beta-l-threo-pentapyranosyl-4''-ulose diphosphate to UDP-alpha-d-apiose and simultaneously to UDP-alpha-d-xylose. The UDP-alpha-d-apiose that is formed is unstable and is converted to alpha-d-apio-furanosyl-1,2-cyclic phosphate and UMP. High-resolution real-time NMR spectroscopy is a powerful tool for the direct and quantitative characterization of previously undetected transient and labile components formed during a complex enzyme-catalyzed reaction.
منابع مشابه
The biosynthesis of the branched-chain sugar d-apiose in plants: functional cloning and characterization of a UDP-d-apiose/UDP-d-xylose synthase from Arabidopsis.
d-Apiose is a plant-specific branched-chain monosaccharide found in rhamnogalacturonan II (RG-II), apiogalacturonan, and several apioglycosides. Within RG-II, d-apiose serves as the binding site for borate, which leads to the formation of cross-links within the wall. Biochemical studies in duckweed and parsley have established that uridine 5'-diphospho-d-apiose (UDP-d-apiose) is formed from UDP...
متن کاملIsotope Probing of the UDP‐Apiose/UDP‐Xylose Synthase Reaction: Evidence of a Mechanism via a Coupled Oxidation and Aldol Cleavage
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 UDP-α-d-apiose (UDP-Api). We examined the mechanism of UDP-Api/UDP-α-d-xylose synthase (UAXS) with site-selectively 2 H-labeled and deoxygenated substrates. The analogue UDP-2...
متن کاملDevelopmental Control of Apiogalacturonan Biosynthesis and UDP-Apiose Production in a Duckweed.
Vegetative fronds of Spirodela polyrrhiza were induced to form dormant turions by the addition of 1 micromolar abscisic acid or by shading. The cell wall polymers of fronds contained a high proportion of the branched-chain pentose, d-apiose (about 20% of total noncellulosic wall sugar residues), whereas turion cell walls contained only trace amounts (about 0.2%). When the fronds were fed d-[(3)...
متن کاملA fluoro analogue of UDP-α-D-glucuronic acid is an inhibitor of UDP-α-D-apiose/UDP-α-D-xylose synthase.
UDP-2F-glucuronic acid was synthesized and analyzed as a mechanistic probe to investigate the ring contraction step catalyzed by UDP-d-apiose/UDP-d-xylose synthase (AXS).
متن کاملDepletion of UDP-D-apiose/UDP-D-xylose synthases results in rhamnogalacturonan-II deficiency, cell wall thickening, and cell death in higher plants.
D-apiose serves as the binding site for borate cross-linking of rhamnogalacturonan II (RG-II) in the plant cell wall, and biosynthesis of D-apiose involves UDP-D-apiose/UDP-D-xylose synthase catalyzing the conversion of UDP-D-glucuronate to a mixture of UDP-D-apiose and UDP-D-xylose. In this study we have analyzed the cellular effects of depletion of UDP-D-apiose/UDP-D-xylose synthases in plant...
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ورودعنوان ژورنال:
- Carbohydrate research
دوره 344 9 شماره
صفحات -
تاریخ انتشار 2009