A NOVEL CHYMOTRYPSIN-LIKE SERINE PROTEINASE FROM HUMAN LUNG

A novel chymotrypsin-like serine proteinase with an M(r) of 30000 has been isolated from human lung tissue. The enzyme was active on both th e synthetic substrate Suc-Ala-Ala-Pro-Phe-SBzl and azocasein, with a p H optimum of 8.0 and a preference for high concentrations of NaCl for maximum activity The proteinase was inhibited by diisopropyl-fluoropho sphate, tosyl-phenylalanyl-chloromethane, chymostatin, soybean trypsin inhibitor, alpha-1-anti-chymotrypsin, and alpha-2-macroglobulin. It w as not inhibited by C-1 inhibitor or aprotinin. An N-terminal sequence of IIGGTESKPDSRPYMALLQIVEPAVH indicated that this enzyme is a member of a superfamily of serine proteinases comprising cathepsin G, chymase , and the granzymes; however, it is clearly distinct from these enzyme s on the basis of both physical and chemical properties.