PRSS3, also known as trypsin-3, is a member of the trypsin family of serine proteases. It is specialized for the degradation of trypsin inhibitors and may be involved in defensin processing, including DEFA5. This protein is expressed in the brain and pancreas and is resistant to common trypsin inhibitors. It is active on peptide linkages involving the carboxyl group of lysine or arginine. Compared to PRSS1 and 2, one intriguing feature of PRSS3 is its resistance to polypeptide trypsin inhibitors, such as the Kunitz-type soybean trypsin inhibitor or the Kazal-type pancreatic secretory trypsin inhibitor. Recombinant human PRSS3, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.