Prss22, also known as brain-specific serine protease 4, is identified brain-specific expression gene. Brain-specific serine protease 4(BSSP-4) and brain serine protease 2 (BSP-2) are different names given for the same serine protease that is encoded by the Prss22 gene. This protein is preferentially expressed in epithelium-rich tissues such as the lung and eye. Recombinant mouse Prss22, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques