The Dissociation of α2-Plasmin-Inhibitor-Plasmin Complex to Active Plasmin by SDS Treatment

Abstract

α2-PI has been demonstrated to be the physiologically most important inhibitor to plas. sin in plasma [1–3], it is a single-chain glycoprotein with molecular weight of about 68,000 [2,4] and inhibits proteolytic activity of plasmin by forming a 1:1 stoichiometric complex which is enzymatically inactive and hardly dissociated by dodecyl sulfate under reducing conditions [5]. α2-PI has been classified as a member of the serine protease inhibitor super family (SERPINS) [6] to which plasminogen activator inhibitor type 1 (PAI-1) also belongs. These protease inhibitors have many similar points in their ways to react with their target enzymes. It has been reported that the complex between PAI-1 and tissue plasminogen activator (t-PA) shows enzymatic activity in zymography [7]. Recently it was also shown that PAI-1 lost its inhibitory activity and was cleaved at the reactive site by PAs after SDS treatment [8]. The latter phenomenon may be responsible for tPA-PAI-1 complex to express enzymatic activity in zymography [8]. Since both PAI-1 and α2-PI are members of SERPINS, it is naturally considered whether SDS has similar effects on α2-PI molecule. We, therefore, investigated the effect of SDS on both α2-PI and α2-PI-plasmin complex in the present study. We also discuss the possible mechanism for α2-PI-plasmin complex to possess enzymatic activity in zymography.