Airway Trypsin-like Protease/HAT: ProductsHAT was initially purified from the sputum of patients with chronic airway diseases. Subsequent cloning revealed it as a member type II transmembrane serine proteases. HAT has been shown to induce PAR-2 mediated IL-8 release in psoriasis vulgaris and increase mucin expression in airway epithelial cells. Located in the cells of the submucosal serous glands of the bronchi and trachea, the isolated enzyme had the N-terminal sequence of ILGGTEAEEG, which corresponded to the start of the C-terminal catalytic domain (residues 187 to 418) of the deduced sequence. The N-terminal region consisted of a short cytoplasmic tail (residues 1 to 20), a transmembrane domain (residues 21 to 41), and a SEA domain (residues 44 to 164). The ectodomain of HAT is expressed and the active enzyme is purified.