Heterologous expression in Pichia pastoris and characterization of a β-glucosidase from the xylophagous cockroach Panesthia angustipennis spadica displaying high specific activity for cellobiose

A β-glucosidase (BG), PaBG1b, from the xylophagous cockroach Panesthia angustipennis spadica was heterologously expressed in the methylotrophic yeast Pichia pastoris, purified, and biochemically characterized. Post-translational modification and N-terminal sequencing analysis demonstrated that the expression product was comprised of two polypeptides with different N-terminal sequences, presumably due to the presence of lysine-arginine (KR) sequence in the putative mature region. Substrate specificity analysis showed that PaBG1b hydrolyzed a broad range of substrates including cellohexaose, with the preference for aryl β-d-fucosyl linkage and laminaribiose. Although the glucose tolerance of PaBG1b was moderate (Ki = 200.3 ± 1.1 mM), PaBG1b demonstrated high specific activity and catalytic efficiency towards cellobiose with Vmax and kcat/Km values of 436.7 ± 6.3 U/mg and 109.8 mM−1 s−1, respectively. In addition, PaBG1b was not inhibited by cellobiose up to the highest concentration tested (100 mM). Collectively, our work demonstrates that PaBG1b is a potentially valuable BG for commercial bioethanol production from cellulose.