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Abstract Detail


Cell Walls

Chatterjee, Mohor [1], Zeng, Wei [2], Faik, Ahmed [2].

Identification and characterization of a glucuronosyltransferase activity involved in glucurono(arabino)xylan biosynthesis in Wheat.

Cell walls in cereals are classified as type II cell walls and predominantly have glucurono(arabino)xylan (GAX) as a major hemicellulose (~35%). GAX consists of a β-(1,4)-D-xylan backbone that is substituted mainly by α-glucuronic acid residues on C-2 positions and by α-arabinofuranose on C-3 positions. Cellulose microfibrils (~20%) in type II walls are cross-linked by β-(1,3)(1,4)-glucan (~30%). In contrast to many hemicelluloses for which the biosynthetic pathways have been elaborated and genes cloned, the biosynthesis of GAX have received relatively little attention. The xylan synthase (XylS) and glucuronosyltransferase (GlcAT) genes have not been identified yet.
The goal of this work is to understand the enzymology of GAX biosynthesis by focusing on the identification and characterization of the glucuronosyltransferase activity that is specific for GAX biosynthesis in wheat. Golgi-enriched microsomes from etiolated wheat seedlings incorporated [14C]GlcA from UDP-[14C]GlcA into ethanol-insoluble products in presence of UDP-Xyl. The products formed are degraded by an endoxylanase specific to wheat arabinoxylan but not by other hydrolases. The [14C]-radiolabel released by total acid hydrolysis was solely associated with glucuronic acid as indicated by analysis on CarboPac PA10 columns using a Dionex system. The activity was partially solubilized with detergents but most of the activity remained tightly associated with the membranes. The activity transferred [14C]GlcA specifically onto xylans added exogenously suggesting that glucuronosyltransferase can act independently from XylS. Purification of this activity is underway.


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1 - Ohio University, Environmental and Plant Biology, 512 Porter Hall, Ohio University, Athens, Ohio, 45701, USA
2 - Ohio University, Environmental and Plant Biology

Keywords:
glucuronosyltransferase
glucurono(arabino)xylan
Cereals
glycosyltransferase
cell wall.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P17023
Abstract ID:1094


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