Effect of Glycosylation of β-Glucuronidase on its Catalytic Properties in Ionic Liquids

H. Tang, B. Wei, S. Huang, M. S. Ahmed, H. Yang, K. Lou, Y. Shi, X. Feng and C. Li

Abstract
The purification of glycosylated recombinant b-glucuronidase from Pichia pastoris GS115 (PGUS-P) was investigated by a novel two-step process: ammonium sulfate precipitation and molecular sieve chromatography. The highest purification fold obtained was 66.79. The catalytic properties of glycosylated PGUS-P in hydrophobic ionic liquids (ILs)/buffer biphasic system were investigated. A 2.2-fold enhancement in the catalytic efficiency was observed using 50% (v/v) 1-butyl-3-methylimidazolium hexafluorophosphate, in comparison with the acetate buffer medium. When compared with the glycosylated PGUS-P, the deglycosylated enzyme at T55 and T65 exhibited low activity and low thermal stability in both ILs and acetate buffer. It was also observed that ILs had effect on the pH profile of deglycosylated PGUS-P — the optimum pH was extended from 5.0 (acetate buffer) to 5.0-7.0 (ILs). Therefore, this study indicates that the glycosylation of PGUS-P plays an important role in both catalytic activity and stability in hydrophobic ionic liquids (ILs)/buffer biphasic system.

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Keywords
β-glucuronidase, glycosylation, ionic liquids, thermostability