Cloning of a Gene Encoding Exoglucanase CBH II from Aspergillus niger and Its Expression in Picchia pastoris

摘要

A gene encoding an exo-β-1,4-glucanase was isolated from Aspergillus niger and designated as CBH II with a length of 1,548 bp, encoding a putative protein of 515 amino acid residues with a predicted molecular mass of 53.9kDa. The deduced amino acid sequence encoded by CBH II showed 92 % homology with the sequence of a not-well-characterized cellulase encoded by cbhB. This putative gene product is homologous to fungal cellobiohydrolases in family 7 of glycosyl hydrolases. The CBH II gene was successfully expressed in Pichia pastoris GS115. The recombinant enzyme was found to be highly glycosylated and the molecular weight of approximately 67kDa according to SDS-PAGE. Optimal temperature and pH of the recombinant enzyme were 60 and 7.0, respectively. And it maintained good stability below 80 ℃ and at pH 3.0-8.0.