Structure and possible biological roles of Lp(a).

Lipoprotein(a) [Lp(a)] is a plasma macromolecular complex that is assembled from low-density lipoproteins (LDL) and a large hydrophilic glycoprotein, named apolipoprotein(a) [apo(a)], linked by a disulfide bond to apolipoprotein B-100. Apo(a) is formed by different structural domains one of which is present in multiple copies, the number of which is determined by variation in the hypervariable apo(a) gene. Sequence homology of apo(a) with plasminogen may explain the competition of Lp(a) for some physiological functions of plasminogen in the coagulation and fibrinolytic cascade in vitro. There is evidence that high plasma levels of Lp(a) may have atherogenic and/or thrombogenic potential. More work will have to be done to understand the exact role of Lp(a) in atherogenesis, to evaluate the potential synergy between Lp(a) and LDL in promoting coronary artery disease, and to assess the therapeutic benefits of a reduction of Lp(a) levels.