Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 34, Pages 15293-15298Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1005732107
Keywords
cell wall degradation; fluorescence quantification; pectate lyase; xylanase; arabinofuranosidase
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Funding
- UK Biotechnology and Biological Sciences Research Council [BB/E014364/1]
- BBSRC [BB/E014364/1, BB/E015190/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/E014364/1, BB/E015190/1] Funding Source: researchfish
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Cell wall degrading enzymes have a complex molecular architecture consisting of catalytic modules and noncatalytic carbohydrate-binding modules (CBMs). The function of CBMs in cell wall degrading processes is poorly understood. Here, we have evaluated the potential enzyme-targeting function of CBMs in the context of intact primary and secondary cell wall deconstruction. The capacity of a pectate lyase to degrade pectic homogalacturonan in primary cell walls was potentiated by cellulose-directed CBMs but not by xylan-directed CBMs. Conversely, the arabinofuranosidase-mediated removal of side chains from arabinoxylan in xylan-rich and cellulose-poor wheat grain endosperm cell walls was enhanced by a xylan-binding CBM but less so by a crystalline cellulose-specific module. The capacity of xylanases to degrade xylan in secondary cell walls was potentiated by both xylan- and cellulose-directed CBMs. These studies demonstrate that CBMs can potentiate the action of a cognate catalytic module toward polysaccharides in intact cell walls through the recognition of nonsubstrate polysaccharides. The targeting actions of CBMs therefore have strong proximity effects within cell wall structures, explaining why cellulose-directed CBMs are appended to many noncellulase cell wall hydrolases.
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