Lysine-binding heterogeneity of Lp(a): consequences for fibrin binding and inhibition of plasminogen activation.
Lipoprotein(a) [Lp(a)] is recognized as an independent risk factor for atherosclerosis. Lp(a) consists of a LDL-like moiety with an additional glycoprotein, apo(a), linked to apolipoprotein B-100. Apo(a) has a high homology with plasminogen (Pg). In vivo, Pg is activated on a fibrin surface by tissue Pg activator (tPA). We prepared Lp(a) from plasma by sequential ultracentrifugation followed by lysine-sepharose affinity chromatography. We found that a changing (donor dependent) fraction of the Lp(a) did not bind to lysine-sepharose. This fraction, designated Lp(a)lys-, was further purified using gel filtration. Bound Lp(a) [Lp(a)lys+] was eluted with 0.2 M EACA. Apo(a) isoforms in both fractions were identical. In contrast Lp(a)lys+ inhibited Pg activation by tPA in vitro (IC50% 20 mg/l), whereas Lp(a)lys- did not. In addition Lp(a)lys- did not bind to CNBr-digested fibrinogen whereas Lp(a)lys+ did (Kd, app = 0.2 nM). Therefore we conclude that a changing donor dependent fraction of human plasma Lp(a) does not inhibit Pg activation in vitro and does not bind to CNBr-digested fibrinogen.
Bas Leerink
C
C
Department of Clinical Chemistry, University Hospital Utrecht, The Netherlands.
Duif
P F
PF
Gimpel
J A
JA
Kortlandt
W
W
Bouma
B N
BN
van Rijn
H J
HJ
D001665:Binding Sites; D002846:Chromatography, Affinity; D005337:Fibrin / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D017270:Lipoprotein(a) / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism*; D011485:Protein Binding; D012685:Sepharose / Q000031:analogs & derivatives
D017270:Lipoprotein(a); C030675:lysine-sepharose; D005337:Fibrin; D010958:Plasminogen; D012685:Sepharose; D008239:Lysine