N-glycosylation affects the proper folding, enzymatic characteristics and production of a fungal ß-glucosidase.

Heterologous expression of ß-glucosidase is one of the approaches to enhance the efficiency of fungal cellulase preparations. It has been reported that N-glycosylation affects the structure framework, function and stability of proteins. In this study, a ß-glucosidase from Aspergillus terreus (GenBank: XP_001216552, BglS) was heterologously expressed in Pichia pastoris and Trichoderma reesei. The four asparagine residues were all linked with high-mannose-type oligosaccharides in P. pastoris, whereas only N224 carried high-mannosetype glycan in T. reesei (the other three sites carried one N-acetylglucosamine). The long N-glycan chains on PpBglS weakened its substrate affinity, activity and thermostability. The moderate post-translational and post-secretory glycan modification in T. reesei makes it a suitable expression system for BglS. The N224 glycan played a critical role in BglS folding. The elucidation of the correlation between the different N-glycosylation patterns of BglS and their corresponding enzymatic characteristics is an important step towards improving the activity, thermostability and even production of heterologous ß-glucosidase by glycan engineering.