Patent ID: 8003362

Claim:
A method to produce active clostripain comprising: (a) incubating an Escherichia coli cell containing an expression cassette under conditions that cause the cell to produce clostripain inclusion bodies, wherein the expression cassette comprises a promoter operably linked to an open reading frame that encodes a peptide consisting of a tag linked to clostripain, wherein the tag is selected from the group consisting of SEQ ID NOs:17 and 25, and wherein the clostripain is selected from the group consisting of SEQ ID NO:28, amino acids 28-526 of SEQ NO:28, SEQ ID NO:29, and a variant of SEQ ID NO:29, wherein the variant of SEQ ID NO:29 has at least 98% sequence identity to SEQ II) NO:29; (b) harvesting the clostripain inclusion bodies from the Escherichia coli cell; and (c) solubilizing the clostripain inclusion bodies in an 8 M urea solution; and (d) diluting said urea solution to a final solution to a final urea concentration of less than 3 M to produce active clostripain.