Report

Revealing Nature’s Cellulase Diversity: The Digestion Mechanism of Caldicellulosiruptor bescii CelA

Science  20 Dec 2013:
Vol. 342, Issue 6165, pp. 1513-1516
DOI: 10.1126/science.1244273

You are currently viewing the abstract.

View Full Text

Via your Institution

Log in through your institution

Log in through your institution


An Enzyme Drill

Cellulase enzymes degrade the cell walls of plants by breaking down cellulose into its constituent sugar fragments and thus have attracted interest for biofuels production. Using transmission electron microscopy Brunecky et al. (p. 1513; see the Perspective by Berlin) discovered that an especially active cellulase, CelA, from Caldicellulosiruptor bescii bacteria does not move along the surface of the substrate, but drills into the cellulose to form cavities.

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.

View Full Text

Related Content