Abstract
Rhamnogalacturonan I (RG-I) is a pectic polysaccharide in primary cell walls. RG-I has a backbone consisting of rhamnose and galacturonic acid residues. The rhamnose residues are substituted with arabinan, galactan, and arabinogalactan side chains. Arabinosyl residues of arabinan and arabinogalactan are mainly arabinofuranosyl (Araf) form.
UDP-Arabinopyranose (UDP-Arap) has been used for the biosynthesis of arabinan. Nunan and Scheller and we reported that a single [14C]Arap residue was incorporated into the exogenous acceptor when UDP-[14C]Arap was used as a donor. To study the biosynthesis of arabinan, we developed an assay to measure (1-5)-α-arabinan synthase activity in Golgi membranes from mung bean using UDP-Araf instead of UDP-Arap as a donor substrate and fluorescent-labeled arabino-oligosaccharides as acceptors. As the results, (1-5)-linked arabinofuranosyl oligosaccharides were formed.
