Expression and Purification of Bovine Enterokinase Light Chain in Recombinant Escherichia coli

A codon optimized sequence coding light chain of bovine enterokinase gene(sBEKLC) was synthesized,and it was fused with DsbA to construct the expression vector(pET39-sBEKLC).Then,the plasmid was transformed into E.coli BL21(DE3) for expression.The strain was cultured in LB medium containing 30 μg/mL kanamycin at 37 ℃.When cell density(D 600) reached 0.5,IPTG was added to reach final concentration of 0.1 mM.After continued cultivation at 28 ℃ for 6 hours,cells were harvested,the volumetric productivity of fusion protein reached 151.2 mg/L,i.e.80.6 mg/L sBEKLC.The cold osmotic shock technique was successfully used to extract sBEKLC from periplasmic space,and nickel affinity chromatography was employed to obtain mature sBEKLC.Finally,about 6.8 mg of sBEKLC was purified from 1 liter fermentation broth and the enzyme activity of sBEKLC was well detected.