Production of a recombinant bovine enterokinase catalytic subunit in the methylotrophic yeast Pichia pastoris

We describe the heterologous expression of a 26.3 kD protein containing the catalytic domain of bovine enterokinase (EK(L)) in the methylotrophic yeast Pichia pastoris. A highly active protein is secreted and glycosylated, and it has the native amino-terminus of EK(L). The cDNA encoding EK(L) was cloned with the protease cleavage site following the alpha mating factor prepro secretion signal from Saccharomyces cerevisiae, The secreted EK(L) was easily purified from the few native proteins found in the P. pastoris fermentation supernatant, using ion exchange and affinity chromatography, The yield of the purified EK(L) was 6.3 mg per liter of fermentation culture, This is significantly higher than previous reports of expressions in E. coli and COS cells, The ability of this highly specific protease to cleave immediately after the carboxyl-terminal residue of the (Asp)(4)-Lys recognition sequence allows regeneration of native aminoterminal residues of recombinant proteins, Its application is demonstrated by the removal of thioredoxin (TrxA), and polyhistidine fusion partners from proteins of interest.