The GH67 _-glucuronidase of Paenibacillus curdlanolyticus B-6 removes hexenuronic acid groups and facilitates biodegradation of the model xylooligosaccharide hexenuronosyl xylotriose
Date
2015
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Article
Publisher
Elsevier Inc.
Journal Title
The GH67 _-glucuronidase of Paenibacillus curdlanolyticus B-6 removes hexenuronic acid groups and facilitates biodegradation of the model xylooligosaccharide hexenuronosyl xylotriose
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Abstract
4-O-Methylglucuronic acid (MeGlcA) side groups attached to the xylan backbone through _-1,2 linkages are converted to hexenuronic acid (HexA) during alkaline pulping. _-Glucuronidase (EC 3.2.1.139) hydrolyzes 1,2-linked MeGlcA from xylooligosaccharides. To determine whether _-glucuronidase can also hydrolyze HexA-decorated xylooligosaccharides, a gene encoding _-glucuronidase (AguA) was cloned from Paenibacillus curdlanolyticus B-6. The purified protein degraded hexenuronosyl xylotriose (_X3), a model substrate prepared from kraft pulp. AguA released xylotriose and HexA from _X3, but the Vmax and kcat values for _X3 were lower than those for MeGlcA, indicating that HexA side groups may affect the hydrolytic activity. To explore the potential for biological bleaching, _X3 degradation was performed using intracellular extract from P. curdlanolyticus B-6. The intracellular extract, with synergistic _-glucuronidase and _-xylosidase activities, degraded _X3 to xylose and HexA. These results indicate that _-glucuronidase can be used to remove HexA from _X3 derived from pulp, reducing the need for chemical treatments in the pulping process. � 2015 Elsevier Inc.
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Enzyme and Microbial Technology