title: [Study of the complex between porcine plasmin and alpha2-macroglobulin (author's transl)].
abstract: Porcine plasmin (EC 3.4.21.7) is obtained from plasminogen activated by human urokinase. This enzyme can bind, in an equimolecular ratio, to an alpha2-macroglobulin isolated from porcine serum. The number of active sites of plasmin has been determined through a burst titration of nitroaniline during the presteady-state hydrolysis of an amide substrate (N-alpha-carbobenzoxy-L-arginine-p-nitroanilide). The kinetic constants relative to a very sensitive ester substrate (N-alpha-carbobenzoxy-L-lysine nitrophenylester) hydrolysis have been measured. The binding of plasmin to alpha2-macroglobulin results in a complete inhibition of proteolytic activity, a reduction of active sites number and a decrease of esterolytic activity towards this substrate. In the complex, the residual activity (about 60%) is protected from protein inhibitors. Absorbance difference spectra show that 1 mol of alpha2-macroglobulin binds 1 mol of plasmin and 2 mol of trypsin. When plasmin is first bound to alpha2-macroglobulin, only 1 mol of trypsin can gain access tothe second site without removing the plasmin, showing that a steric hindrance is implicated in the inhibition performed by alpha2-macroglobulin binding.
mesh_terms: D000495:Allosteric Site; D000577:Amides / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D005341:Fibrinolysin / Q000378:metabolism*; D007700:Kinetics; D009596:Nitrophenols / Q000378:metabolism; D011485:Protein Binding; D013552:Swine; D013696:Temperature; D014357:Trypsin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: D000577:Amides; D009596:Nitrophenols; D000511:alpha-Macroglobulins; D014357:Trypsin; D005341:Fibrinolysin
vernacular_title: Etude du complexe plasmine-alpha2-macroglobuline de porc