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Revealing nature's cellulase diversity: the digestion mechanism of Caldicellulosiruptor bescii CelA.

Science (New York, N.Y.) (2013-12-21)
Roman Brunecky, Markus Alahuhta, Qi Xu, Bryon S Donohoe, Michael F Crowley, Irina A Kataeva, Sung-Jae Yang, Michael G Resch, Michael W W Adams, Vladimir V Lunin, Michael E Himmel, Yannick J Bomble
ABSTRACT

Most fungi and bacteria degrade plant cell walls by secreting free, complementary enzymes that hydrolyze cellulose; however, some bacteria use large enzymatic assemblies called cellulosomes, which recruit complementary enzymes to protein scaffolds. The thermophilic bacterium Caldicellulosiruptor bescii uses an intermediate strategy, secreting many free cellulases that contain multiple catalytic domains. One of these, CelA, comprises a glycoside hydrolase family 9 and a family 48 catalytic domain, as well as three type III cellulose-binding modules. In the saccharification of a common cellulose standard, Avicel, CelA outperforms mixtures of commercially relevant exo- and endoglucanases. From transmission electron microscopy studies of cellulose after incubation with CelA, we report morphological features that suggest that CelA not only exploits the common surface ablation mechanism driven by general cellulase processivity, but also excavates extensive cavities into the surface of the substrate. These results suggest that nature's repertoire of cellulose digestion paradigms remain only partially discovered and understood.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cellulase from Trichoderma reesei ATCC 26921, lyophilized powder, ≥1 unit/mg solid
Supelco
Cellulose, powder, for column chromatography
Sigma-Aldrich
Avicel® PH-101, tested according to Ph. Eur.
Supelco
Cellulose, DFS-0, microcrystalline, suitable for thin layer chromatography (TLC)
Sigma-Aldrich
Cellulase from Trichoderma reesei, aqueous solution, ≥700 units/g
Sigma-Aldrich
Cellulase from Trichoderma sp., BioReagent, suitable for plant cell culture, 3-10 units/mg solid
Sigma-Aldrich
Cellulose, fibers, (medium)
Supelco
Cellulose, acid washed, powder, for column chromatography
Supelco
Cellulose, DS-0, powder, suitable for thin layer chromatography (TLC)
Supelco
Cellulose, acid washed, from spruce, for column chromatography
Supelco
Avicel® PH-101, ~50 μm particle size
Sigma-Aldrich
Cellulose, microcrystalline, powder, 20 μm
Sigma-Aldrich
Cellulose, colloidal, microcrystalline
Sigma-Aldrich
Cellulose, microcrystalline, powder
Sigma-Aldrich
Cellulase from Trichoderma sp., powder, ≥5,000 units/g solid
Sigma-Aldrich
α-Cellulose, BioReagent, suitable for insect cell culture
Sigma-Aldrich
α-Cellulose, powder
Sigma-Aldrich
Cellulase from Aspergillus sp., aqueous solution
Sigma-Aldrich
Cellulase from Aspergillus niger, powder, off-white, ~0.8 U/mg
Sigma-Aldrich
Sigmacell Cellulose, Type 101, Highly purified, fibers
Sigma-Aldrich
Sigmacell Cellulose, Type 20, 20 μm
Sigma-Aldrich
Sigmacell Cellulose, Type 50, 50 μm
Sigma-Aldrich
Cellulase from Aspergillus niger, powder, ≥0.3 units/mg solid