Generation of a vasoactive peptide by a neutral protease of human neutrophil leukocytes

Neutrophil leukocyte lysosomes contain a neutral protease capable of cleaving a peptide from kininogen. The protease has a molecular weight of about 27,000-28,000, as determined by SDS-disc gel electrophoresis and gel filtration in the presence of guanidine-HCl. Its S-value is 2.7 and the pI 10.0-11.8. Although homogeneous by some criteria (sucrose density gradient ultracentrifugation, gel filtration in Sephadex G-75, SDS-disc gel electrophoresis, immunoelectrophoresis), the protease is heterogeneous by other criteria (cation exchange chromatography, cationic disc gel electrophoresis and isoelectric focusing). The heterogeneity is attributable to charge isomerism. The enzyme is inhibited by DFP and a number of chloromethyl ketone inhibitors. It is also inhibited by the plasma protease inhibitors alpha1-antitrypsin, alpha2-macroglobulin and antithrombin III. The generated peptide has chemical and pharmacological properties similar to the undecapeptide methionyl-lysyl-bradykinin, but probably contains one or two additional amino acids.