Deglycosylation significantly affects the activity, stability and appropriate folding of recombinant Aspergillus niger α-L-rhamnosidase expressed in Pichia pastoris

Glycosylation plays a critical role in regulating activity, stability, and correct folding of enzymes. In this study, recombinant Aspergillus niger α-L-rhamnosidase (r-Rha1) was employed to explore the impact of glycosylation in Pichia pastoris on the enzymatic properties and protein folding . β-elimination reaction and deglycosylase treatment assays demonstrated that r-Rha1 undergoes primarily N-glycosylation. The deglycosylated r-Rha1 was prepared in two ways: treating with Endoglycosidase F 1 after expression (referred to as r-Rha1- vitro ), or inhibiting intracellular glycosylation using tunicamycin (referred to as r-Rha1- vivo ). Deglycosylation resulted in a 0.22-fold decrease in activity for r-Rha1- vitro and due to its slower turnover rate, r-Rha1- vivo showed a 0.73-fold decrease in activity. r-Rha1- vitro maintained the similar optimal temperature as r-Rha1, r-Rha1- vivo displayed a 10 °C lower optimal temperature. Compared to the decreased extent of r-Rha1- vitro in t 1/2 at 55 °C, 60 °C, and 65 °C and T m , chemical interferent deglycosylation in vivo showed a more profound impact on r-Rha1. Analyses based on circular dichroism, fluorescence spectroscopy, and differential scanning calorimetry revealed significant changes in the structure and thermodynamic stability of r-Rha1- vivo , accounting for its marked decline in activity and stability. The significant and unpredictable structure changes of r-Rha1- vivo proved the essential role of glycosylation for appropriate folding in P. pastoris .