The aim of this work was to study the contribution of the N-terminal structure to cellulase catalytic performance. A wild-type cellulase (BaCel5) of glycosyl hydrolase (GH) family 5 from Bispora antennata and two hybrid enzymes (BaCel5(127) and BaCel5(167)) with replacement of the N-terminal (beta alpha)(3) (127 residues) or (beta alpha)(4) (167 residues)-barrel with the corresponding sequences of TeEgl5A from Talaromyces emersonii were produced in Pichia pastoris and biochemically characterized. BaCel5 exhibited optimal activity at pH 5.0 and 50 degrees C but had low catalytic efficiency (25.4 +/- 0.8 mL s(-1) mg(-1)). In contrast, BaCel5(127) and BaCel5(167) showed similar enzymatic properties but improved catalytic performance. When using CMCNa, barley b-glucan, lichenan, and cellooligosaccharides as substrates, BaCel5(127) and BaCel5(167) had increased specific activities and catalytic efficiencies by similar to 1.8-6.7-fold and similar to 1.0-4.7-fold, respectively. The catalytic efficiency of BaCel5(167) was even higher than that of parental proteins. The underlying mechanism was analyzed by molecular docking and molecular dynamic simulation. (C) 2016 Elsevier Ltd. All rights reserved.