title: Inverting character of alpha-glucuronidase A from Aspergillus tubingensis.
abstract: Alpha-glucuronidase A from Aspergillus tubingensis was found to be capable of liberating 4-O-methyl-D-glucuronic acid (MeGlcA) only from those beechwood glucuronoxylan fragments in which the acid is attached to the non-reducing terminal xylopyranosyl residue. Reduced aldotetrauronic acid, 4-O-methyl-D-glucuronosyl-alpha-1,2-D-xylopyranosyl-beta-1,4-xylopyranosyl-beta-1,4-xylitol, was found to be a suitable substrate to follow the stereochemical course of the hydrolytic reaction catalyzed by the purified enzyme. The configuration of the liberated MeGlcA was followed in a D(2)O reaction mixture by (1)H-NMR spectroscopy. It was unambiguously established that MeGlcA was released from the substrate as its beta-anomer from which the alpha-anomer was formed on mutarotation. This result represents the first experimental evidence for the inverting character of a microbial alpha-glucuronidase, a member of glycosyl hydrolase family 67 (EC 3.1.1.139).
authors.affiliation: Institute of Chemistry, Slovak Academy of Sciences, 842 38 Bratislava, Slovak Republic. chempbsa@savba.sk
authors.forename: P
authors.initials: P
authors.lastname: Biely
authors.lastname: de Vries RP
authors.forename: M
authors.initials: M
authors.lastname: Vrsanská
authors.forename: J
authors.initials: J
authors.lastname: Visser
mesh_terms: D001230:Aspergillus / Q000201:enzymology*; D002240:Carbohydrate Sequence; D005965:Glucuronates / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D013237:Stereoisomerism; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism
chemical_list: D005965:Glucuronates; D014990:Xylans; C036035:4-O-methylglucuronic acid; C038910:glucuronoxylan; D006026:Glycoside Hydrolases; C096734:alpha-glucuronidase