Expression of Kringle 5 Gene of Human Plasminogen in Pichia pastoris and Antitumor Activity of Expressed Product

Objective To express the kringle 5 gene of human plasminogen (hK5) in Pichia pastoris and determine the antitumor activity of expressed hK5 protein. Methods Design and synthesize hK5 gene according to the codon bias of Pichia pastoris and insert into plasmid p819. Transform the constructed recombinant plasmid p819-8α-hK5 to Pichia pastoris GS115, screen transformants by G418 pressure screening for expression under induction of methanol. The condition for fermentation culture of recombinant Pichia pastoris in shaking flask was optimized. The expressed hK5 protein was purified by DEAE-Sepharose chromatography and G75 gel filtration, and evaluated for inhibitory activity to H22 tumor in KM mouse model. Results Two transformants for high expression of hK5 protein was screened. The expression level of hK5 protein in Pichia pastoris cultured in shaking flask under the optimized condition was more than 150 mg / L. The expressed hK5 protein reached a purity of more than 95. 0% after purification and inhibited the growth of H22 tumor in KM mice. Conclusion hK5 protein was highly expressed in Pichia pastoris and showed good antitumor activity.