Structure and function of a novel cellulase 5 from sugarcane soil metagenome

ALVAREZ TM; PAIVA JH; RUIZ DM; CAIRO JP; PEREIRA IO; PAIXÃO DA; DE ALMEIDA RF; TONOLI CC; RULLER R; SANTOS CR; SQUINA FM; MURAKAMI MT

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2013 vol. 8 p. 1 - 9

1932-6203

Cellulases play a key role in enzymatic routes for degradation of plant cell-wall polysaccharides into simple and economically-relevant sugars. However, their low performance on complex substrates and reduced stability under industrial conditions remain the main obstacle for the large-scale production of cellulose-derived products and biofuels. Thus, in this study a novel cellulase with unusual catalytic properties from sugarcane soil metagenome (CelE1) was isolated and characterized. The polypeptide deduced from the celE1 gene encodes a unique glycoside hydrolase domain belonging to GH5 family. The recombinant enzyme was active on both carboxymethyl cellulose and B-glucan with an endo-acting mode according to capillary electrophoretic analysis of cleavage products. CelE1 showed optimum hydrolytic activity at pH 7.0 and 50 °C with remarkable activity at alkaline conditions that is attractive for industrial applications in which conventional acidic cellulases are not suitable. Moreover, its threedimensional structure was determined at 1.8 Å resolution that allowed the identification of an insertion of eight residues in the b8-a8 loop of the catalytic domain of CelE1, which is not conserved in its psychrophilic orthologs. This 8-residue-long segment is a prominent and distinguishing feature of thermotolerant cellulases 5 suggesting that it might be involved with thermal stability. Based on its unconventional characteristics, CelE1 could be potentially employed in biotechnological processes that require thermotolerant and alkaline cellulases.