Enzymatic properties of a2-macroglobulin-elastase complex

Natural substrates of human leukocyte elastase (ELF) in the blood are suspected to be fibrinogen and fibrin, although ELF is immediately complexed with a2-macroglobulin (a2M) and other inhibitors. However, the enzymatic activity of a2M ELP complex is not yet clear. This study was undertaken t o clarify the activity of the complex. (1) ELF and a2M were purified respectively, then the a2MOELP complex was prepared. (2) The complex immediately after preparation degraded a specific synthetic substrate of ELF, Suc-Ala-Tyr-Leu-Val-pNA, independently of NaC104 concentration in the reaction medium, different from the mode of action of free ELF. (3) However, the complex could not degraded fibrin or fibrinogen without the addition of NaC104. (4) The amidolytic and fibrinolytic activities of the complex without addition of NaC104 were 45% and 2% of those of free ELF, respectively, and those in the presence of 0.2 M NaC104 were 35% and 45 %, respectively. (5) After incubation at 37°C for over 24 hr, the complex degraded fibrin and fibrinogen as well as synthetic substrate without the addition of NaC104. (6) The inhibition for amidolytic activity of the complex by various inhibitors