4-O-Methylglucuronic acid (MeGlcA) side groups attached to the xylan backbone through alpha-1,2 linkages are converted to hexenuronic acid (HexA) during alkaline pulping. alpha-Glucuronidase (EC 3.2.1.139) hydrolyzes 1,2-linked MeGlcA from xylooligosaccharides. To determine whether alpha-glucuronidase can also hydrolyze HexA-decorated xylooligosaccharides, a gene encoding alpha-glucuronidase (AguA) was cloned from Paenibacillus curdlanolyticus B-6. The purified protein degraded hexenuronosyl xylotriose (Delta X3), a model substrate prepared from kraft pulp. AguA released xylotriose and HexA from Delta X3, but the V-max and k(cat) values for Delta X3 were lower than those for MeGlcA, indicating that HexA side groups may affect the hydrolytic activity. To explore the potential for biological bleaching, Delta X3 degradation was performed using intracellular extract from P. curdlanolyticus B-6. The intracellular extract, with synergistic a-glucuronidase and beta-xylosidase activities, degraded Delta X3 to xylose and HexA. These results indicate that a-glucuronidase can be used to remove HexA from Delta X3 derived from pulp, reducing the need for chemical treatments in the pulping process. (C) 2015 Elsevier Inc. All rights reserved.