The Expression of Bovine Enterokinase Catalytic Subunit in Methylotropic Yeast Pichia pastoris

The objective of the study was to acquire the bovine enterokinase light chain (EK_L) expressed in Pichia pastoris, which would be used in the cleavage and purification of fusion proteins. The fragment of EK_L cDNA was obtained by RT-PCR from a sold bovine´s duodenal mucosa, then cloned into the pUCm-T cloning vector and sequenced. Compared with the sequence deposited in GenBank, the cloned gene sequence is correct. Then the interested gene fragment was inserted into the pPIC9 expression plasmid. The recombinant vector pPIC9-EK_L was linearized and introduced into Pichia pastoris GS115 with the method of PEG1000. The recombinant EK_L was secreted in fermentation supernatant with molecular weight of 36 KDa. The yield of EK_L was 32.8% of total supernatant protein. After separation and purification by STI resin affinity chromatography, the production of rEK_L was about 10.9 ug/mL fermented solution, which had a specific activity of 2.88times107U/mg.