Mode of action of beta-glucuronidase from Aspergillus niger on the sugar chains of arabinogalactan-protein.
A beta-glucuronidase purified from a commercial pectolytic enzyme preparation of Aspergillus niger hydrolyzed about half of the 4-O-methyl-glucuronic acid (4-Me-GlcA) residues located at the nonreducing terminals of (1-->6)-linked beta-galactosyl side chains of the carbohydrate portion of a radish arabinogalactan-protein (AGP) modified by treatment with fungal alpha-L-arabinosidase. Digestion of the alpha-L-arabinosidase-treated AGP with exo-beta-(1-->3)-galactanase released, by exo-fission of beta-(1-->3)-galactosidic bonds in the backbone chains of the AGP, neutral beta-(1-->6)-galactooligosaccharides with various chain lengths and their acidic derivatives substituted at their nonreducing terminals with 4-Me-beta-GlcA groups. In contrast, successive digestion of the alpha-L-arabinosidase-treated AGP with beta-glucuronidase followed by exo-beta-(1-->3)-galactanase liberated much higher amounts of beta-(1-->6)-galactooligomers together with a small portion of short acidic oligomers, mainly 4-Me-beta-GlcA-(1-->6)-Gal and 4-Me-beta-GlcA-(1-->6)-beta-Gal-(1-->6)-Gal. These results indicate that beta-glucuronidase acts upon 4-Me-beta-GlcA residues in long (1-->6)-linked beta-galactosyl side chains of the AGP, whereas short acidic side chains survive the attack of the enzyme.
Haque
Md  Ashraful
M
Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Japan.
Kotake
Toshihisa
T
Tsumuraya
Yoichi
Y
D001234:Aspergillus niger / Q000201:enzymology*; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis*; D002845:Chromatography; D005966:Glucuronidase / Q000378:metabolism*; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D031224:Raphanus / Q000737:chemistry
D002241:Carbohydrates; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins; D005966:Glucuronidase