High-level expression of prolyl endopeptidase in Pichia pastoris using PLA2 as a fusion partner

Abstract

In our previous studies, a prolyl endopeptidase (PEP) gene from Aspergillus oryzae (MOH) was cloned and expressed in Pichia pastoris; however, the recombinant protein expression level of MOH was very low. In the present study, the PEP expression level was successfully improved by constructing fusion expression proteins with four fusion partners, namely, Streptomyces violaceoruber Phospholipase A2 (PLA2), cellulose-binding domain (CBD), small ubiquitin-related modifier (SUMO) and maltose binding protein (MBP). The enzyme activities of the recombinant fusion proteins CLMH, SLMH, MLMH and PLMH were increased to 3.8-, 2.7-, 4.9- and 7.4-fold compared with that of the parent MOH. Moreover, the extracellular protein content of CLMH, SLMH, MLMH, PLMH were 1.42-, 1.25-, 1.67- and 1.83-fold higher compared with that of MOH. Both PLMH and MOH showed the highest activity at pH 5.5, the highest stability at pH 6.0 and maximal activity at 40°C.