Inverting character of family GH115 α-glucuronidases

alpha-Glucuronidases of glycoside hydrolase family 115 of the xylose-fermenting yeast Pichia stipitis and wood-destroying fungus Schizophyllum commune liberate 4-O-methyl-D-glucuronic acid residues from aldouronic acids and glucuronoxylan. The specific activities of both enzymes depended on polymerization degree of the acidic xylooligosaccharides and were inhibited by linear beta-1,4-xylooligosaccharides. These results suggest interaction of the enzyme with several xylopyranosyl residues of the xylan main chain. Using H-1 NMR spectroscopy and reduced aldopentaouronic acid (MeGlcA(3)Xyl(4)-ol) as a substrate, it was found that both enzymes are inverting glycoside hydrolases releasing 4-O-methyl-D-glucuronic acid (MeGlcA) as its beta-anomer. (c) 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.