Strategy for improvement of enteropeptidase efficiency in tag removal processes

Enteropeptidase (synonym: enterokinase, EC 3.4.21.9) is a heterodimeric serine protease of the intestinal brush border that activates trypsinogen by highly specific cleavage of the trypsinogen activation peptide following the sequence (Asp)(4)-Lys. It has also great biotechnological interest because of the unique substrate specificity of the serine protease domain. The high degree of specificity exhibited by enteropeptidase makes it a suitable reagent for cleaving recombinant proteins to remove affinity or other tags. However often unwanted cleavages elsewhere in the protein occurred during cleavage of fusions when high amount of enzyme is required. In this study we have improved the efficiency of fusion proteins cleavage by enteropeptidase by substitution of the Lys residue by Arg in specific cleavage sequence (Asp)(4)-Lys. We have demonstrated that 3-6-fold lower amounts of the catalytic subunit of human and bovine enteropeptidase is required for 95% cleavage of Trx/TRAIL and Trx/FGF-2 fusions with (Asp)(4)-Arg cleavage sequence in comparison to native sequence (Asp)(4)-Lys. As a result, reduced amount of non-specifically cleaved peptide fragments were observed during cleavage of (Asp)(4)-Lys/Arg mutated fusions. These findings overcome limitations of enteropeptidase in tag removal processes during recombinant proteins purification and extend its commercial benefit in the biopharmaceutical industry.