An aminopeptidase of human neutrophil leucocytes--its possible role in enhanced vascular permeability

An aminopeptidase of human leukocyte lysosomes was partially purified by chromatography on SP-Sephadex, Sephadex G-200 and QAE-Sephadex. By QAE-Sephadex and isolelectric focusing it showed microheterogeneity, focusing at pH 3.7 and 4.1. By gel filtration its molecular weight was estimated to be approx. 200,000. The enzyme had leucine amino peptidase activity and pharmacological assays indicated that it converted lysyl- or methionyl-lysyl-bradykinin to bradykinin. Conversion of lysyl-bradykinin to bradykinin could be confirmed also by chromatography on CM-cellulose. When the neutrophil-derived enzyme acted on methionyl-lysyl-bradykinin it increased its effect of enhancing vascular permeability, when injected intradermally into guinea pits. Thus the enzyme may play a role in neutrophil leukocyte-mediated vascular phenomena of the inflammatory reaction.