Purification and properties of a 6-glucuronidase from aspergillus niger

Abstract

Abstract : An experiment was conducted of a B-glucuronidase from Pectinex Ultra SP-L, a commercial pectolytic enzyme preparation from Aspergillus niger, was purified 108-fold by ion-exchange chromatography and gel filtration at Saitama University, Japan. This purified B-glucuronidase should be acted on arabinogalactan-protein (AGP) and released 4-Me-GlcA. Apparent molecular weight (Mr) of the purified enzyme, estimated by denaturing gel electrophoresis and size-exclusion chromatography, were 68,000 and 71,000, respectively, indicating that the enzyme is a monomeric protein. The enzyme exhibited a maximal activity toward these substrates at pH 3.0. A regioisomer, 3-G-6- glucuronosyl-galactose, was unsusceptible to the enzyme. The enzyme acted on a polymer substrate, releasing uronic acid from the carbohydrate moiety of a radish arabinogalactan-protein modified by treatment with fungal a-L- arabinofuranosidase. The enzyme produced acidic oligosaccharides catalyzing the transfer of uronic acid residues of p-nitrophenol B- glucopyranosidase (PNP- GlcA) and 6-O-B-glucuronosyl-galactose to certain exogenous acceptor sugars such as Gal, /V-acetylgalactosamine, Glc, and xylose.