Effect of Pichia pastoris host strain on the properties of recombinant Aspergillus niger endoglucanase, EglB

Aims: The methylotrophic yeast Pichia pastoris is widely used to express foreign proteins fused to secretion signals. As the effect of the expression host on the final protein product is unclear, we compared the properties of an endoglucanase (eglB of Aspergillus niger) expressed in two different P. pastoris strains.
Methodology and results: Full-length cDNA encoding endoglucanase of A. niger strain ATCC10574 was isolated and expressed in P. pastoris X33 (the methanol utilisation plus phenotype, Mut+) and P. pastoris GS115 (slow methanol utilisation, MutS). EglB-GS115 showed the highest activity and stability at 60 °C while EglB-X33 was most active at 50 °C. EglB-X33 was active towards other substrates such as arabinogalactan, guar gum and locust bean gum besides its specific substrate, carboxymethyl cellulose (CMC). However, EglB-GS115 was only active on CMC. The affinity of EglB-X33 towards CMC (Km = 7.5 mg.mL-1 and specific activity 658 U.mg-1) was higher than that of EglB-GS115 (Km = 11.57 mg.mL-1, specific activity 144 U.mg-1).
Conclusion, significance and impact of study: Although eglB was cloned in the same expression vector (pPICZαC), two different characteristics of enzymes were recovered from the supernatant of the different hosts. Thus, expression of recombinant enzyme in different P. pastoris strains greatly affects the physical structure and biochemical properties of the enzyme.

Keywords: cellulase, endoglucanase, glycosylation, methanol utilisation phenotype, recombinant enzyme