Plasma membrane-anchored serine protease that directly induces processing of pro-uPA/PLAU into the active form through proteolytic activity (PubMed:24434139). Seems to be capable of activating ENaC (By similarity). (Microbial infection) In gut epithelial cells, facilitates human coronavirus SARS-CoV-2 infection through, at least, the cleavage of coronavirus spike glycoproteins which activates the glycoprotein for host cell entry. Activated by cleavage and secreted. High levels in pancreatic, gastric, colorectal and ampullary cancer. Very weak expression in normal gastrointestinal and urogenital tract (PubMed:10825129). Coexpressed with ACE2 within mature enterocytes (PubMed:32404436). Proteolytically processed; probably by an autocatalytic mechanism. Belongs to the peptidase S1 family.