Molecular interactions of Leishmania promastigote surface protease with human α2-macroglobulin

Abstract

The interaction of Leishmania promastigote surface protease (PSP) with the plasmatic protease inhibitor α2-macroglobulin (α2M) was investigated. In plasma, solubilized PSP forms covalent complexes only with α2M, at the exclusion of other protease inhibitors. The formation of complexes is accompanied by the proteolytic cleavage of the α2M subunit and by the transition from the ‘slow’ to the ‘fast’ form of α2M. The proteolytic activity of solubilized PSP on azocasein is inhibited by α2M. In contrast, we found no evidence for a specific interaction of α2M with the surface of promastigotes and PSP proteolytic activity on intact cells was not inhibited by α2M.