Identification of a mung bean arabinofuranosyltransferase that transfers arabinofuranosyl residues onto (1, 5)-linked alpha-L-arabino-oligosaccharides.
Arabinofuranosyltransferase activity was identified in Golgi membranes obtained from mung bean (Vigna radiata) hypocotyls. The enzyme transfers the arabinofuranosyl (Araf) residue from UDP-beta-L-arabinofuranose to exogenous (1, 5)-linked alpha-L-arabino-oligosaccharides labeled at their reducing ends with 2-aminobenzamide. The transferred residue was shown, using 1H-nuclear magnetic resonance spectroscopy and alpha-L-arabinofuranosidase treatment, to be alpha-L-Araf and to be linked to O-5 of the nonreducing terminal Araf residue of the acceptor oligosaccharide. The enzyme was nonprocessive because only a single Araf residue was added to the acceptor molecule. Arabino-oligosaccharides with a degree of polymerization between 3 and 8 were acceptor substrates. The 2-aminobenzamide-labeled arabino-tetra- and pentasaccharides were the most effective acceptor substrates analyzed. The enzyme has a pH optimum between 6.5 and 7.0 and its activity is stimulated by Mn2+ and Co2+ ions. The apparent Km and Vmax values of the arabinofuranosyltransferase for UDP-arabinofuranose are 243 microm and 243 pmol min(-1) mg protein(-1), respectively. The highest enzyme activity was detected in the elongating regions of mung bean hypocotyls. The data show that UDP-arabinofuranose is the donor molecule for the generation of arabino-oligosaccharides composed of Araf residues.
Konishi
Teruko
T
Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan.
Ono
Hiroshi
H
Ohnishi-Kameyama
Mayumi
M
Kaneko
Satoshi
S
Ishii
Tadashi
T
D001089:Arabinose / Q000378:metabolism; D007887:Fabaceae / Q000201:enzymology*; D006056:Golgi Apparatus / Q000201:enzymology*; D018546:Hypocotyl / Q000201:enzymology*; D009844:Oligosaccharides / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*; D062367:ortho-Aminobenzoates
D009844:Oligosaccharides; D010940:Plant Proteins; D062367:ortho-Aminobenzoates; D001089:Arabinose; D014166:Transferases; C000219:anthranilamide