Trypsin-like serine protease. Has a preference for extended substrates with basic residues at the P1 position; Arg is preferred over Lys. Active towards calcitonin gene-related peptide and gelatin. Not active towards substance P, vasoactive intestinal peptide, type I collagen or azocasein. Inhibited by leupeptin and bis(5-amidino-2-benzimidazolyl)methane (BABIM). Optimum pH is 8.0-8.5. Oligomer; disulfide-linked. Mononuclear cells within skin, intestine, trachea and lung parenchyma, and polymorphonuclear leukocytes within capillaries and blood. N-glycosylated. Belongs to the peptidase S1 family.