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

• Fusion expression is an effective strategy to improve protein secretion level.
• PLA2 was successfully used as a fusion chaperon for the first time.
• P. pastoris GS115 can be a suitable host for heterogenous expression.

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.

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