Multifunctional cellulolytic auxiliary activity protein HcAA10-2 from Hahella chejuensis enhances enzymatic hydrolysis of crystalline cellulose

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Title
Multifunctional cellulolytic auxiliary activity protein HcAA10-2 from Hahella chejuensis enhances enzymatic hydrolysis of crystalline cellulose
Author(s)
S S Ghatge; A A Telke; T R Waghmode; Y Lee; K W Lee; Doo-Byoung Oh; H D Shin; S W Kim
Bibliographic Citation
Applied Microbiology and Biotechnology, vol. 99, no. 7, pp. 3041-3055
Publication Year
2015
Abstract
The modular auxiliary activity (AA) family of proteins is believed to cause amorphogenesis in addition to oxidative cleavage of crystalline cellulose although the supporting evidence is limited. HcAA10-2 is a modular AA10 family protein (58 kDa) composed of a AA10 module and a family two carbohydrate binding module (CBM2), joined by a long stretch of 222 amino acids of unknown function. The protein was expressed in Escherichia coli and purified to homogeneity. Scanning electron microscopy and X-ray diffraction analysis of Avicel treated with HcAA10-2 provided evidence for the disruption of the cellulose microfibrils (“amorphogenesis”) and reduction of the crystallinity index, resulting in a twofold increase of cellulase adsorption on the polysaccharide surface. HcAA10-2 exhibited weak endoglucanase-like activity toward soluble cellulose and cello-oligosaccharides with an optimum at pH 6.5 and 45 °C. HcAA10-2 catalyzed oxidative cleavage of crystalline cellulose released native and oxidized cello-oligosaccharides in the presence of copper and an electron donor such as ascorbic acid. Multiple sequence alignment indicated that His1, His109, and Phe197 in the AA10 module formed the conserved copper-binding site. The reducing sugar released from Avicel by the endoglucanase Cel5 and Celluclast accompanying HcAA10-2 was increased by four- and sixfold, respectively. Moreover, HcAA10-2 and Celluclast acted synergistically on pretreated wheat straw biomass resulting in a threefold increase in reducing sugar than Celluclast alone. Taken together, these results suggest that HcAA10-2 is a novel multifunctional modular AA10 protein possessing amorphogenesis, weak endoglucanase, and oxidative cleavage activities useful for efficient degradation of crystalline cellulose.
Keyword
AA10 (formerly CBM33)AmorphogenesisEndoglucanaseLytic polysaccharide monooxygenases (LPMOs)Oxidative cleavage
ISSN
0175-7598
Publisher
Springer
DOI
http://dx.doi.org/10.1007/s00253-014-6116-6
Type
Article
Appears in Collections:
Aging Convergence Research Center > 1. Journal Articles
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