activation of plasminogen and apolipoproteins - apo(a)

The major apolipoproteins present in Lp(a) -- the apolipoprotein B or apoB series and the apolipoprotein(a) or apo(a) series -- play different roles in health and disease. ApoB-100 is the portion of the Lp(a) molecule (the ligand) that is recognized by the receptor. Other lipid and apolipoprotein components vary considerably in the LDL complex, but they all interact to maintain the apo B molecule in a specific spatial orientation for receptor binding. The second major Lp(a) apolipoprotein is apo(a), which has been described as a giant mutant of plasminogen. This is because approximately 80% of the amino acid sequence of apo(a) is identical to that of plasminogen. Because of this homology, apo(a) is able to competitively inhibit the surface binding and activation of plasminogen. Blocking plasminogen activation prevents the formation of plasmin, a crucial component in clot lysis. Plasmin is also involved in the activation of a compound referred to as latent transforming growth factor-b (TGF-b), a potent inhibitor of smooth muscle cell growth in the vascular endothelium.
source:Grainger DJ et al. Science