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Query: UNIPROT:Q9UE34 (fibrinogen)
 30,244 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown functional differences in fibrinogen from hyperhomocysteinemic rabbits compared to that in control rabbits. This acquired dysfibrinogenemia is characterized by fibrin clots that are composed of abnormally thin, tightly packed fibers with increased resistance to fibrinolysis. Homocysteine thiolactone is a metabolite of homocysteine (Hcys) that can react with primary amines. Recent evidence suggests that Hcys thiolactone-lysine adducts form in vivo. We now demonstrate that the reaction of Hcys thiolactone with purified fibrinogen in vitro produces fibrinogen (Hcys fibrinogen) with functional properties that are strikingly similar to those we have observed in homocysteinemic rabbits. Fibrinogen purified from homocysteinemic rabbits and Hcys fibrinogen are similar in that (1) they both form clots composed of thinner, more tightly packed fibers than their respective control rabbit and human fibrinogens; (2) the clot structure could be made to be more like the control fibrinogens by increased calcium; and (3) they both form clots that are more resistant to fibrinolysis than those formed by the control fibrinogens. Further characterization of human fibrinogens showed that Hcys fibrin had similar plasminogen binding to that of the control and an increased capacity for binding tPA. However, tPA activation of plasminogen on Hcys fibrin was slower than that of the control. Mass spectrometric analysis of Hcys fibrinogen revealed twelve lysines that were homocysteinylated. Several of these are close to tPA and plasminogen binding sites. Lysines are major binding sites for fibrinolytic enzymes and are also sites of plasmin cleavage. Thus, modification of lysines in fibrinogen could plausibly lead to impaired fibrinolysis. We hypothesize that the modification of lysine by Hcys thiolactone might occur in vivo, lead to abnormal resistance of clots to lysis, and thereby contribute to the prothrombotic state associated with homocysteinemia.
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PMID:Modification of fibrinogen by homocysteine thiolactone increases resistance to fibrinolysis: a potential mechanism of the thrombotic tendency in hyperhomocysteinemia. 1648 40

We have shown that homocysteinemic rabbits have altered fibrinogen that forms fibrin clots with increased resistance to fibrinolysis. Homocysteine thiolactone is a metabolite of homocysteine (Hcys) that can react with amines and introduce a new sulfhydryl group into proteins. Recent evidence suggests that Hcys thiolactone-lysine adducts form in vivo. We have shown that in vitro reaction of Hcys thiolactone with human fibrinogen (Hcys-fibrinogen) alters fibrinogen function in a manner similar to that in homocysteinemic rabbits. Several naturally-occurring mutations that introduce a new cysteine into fibrinogen are associated with clinical thrombosis due to increased resistance of clots to fibrinolysis. In those cases the new cysteine mediates disulfide formation between the mutant fibrinogen and albumin. We now report that Hcys-fibrinogen similarly forms disulfides with albumin in vitro, specifically through sites in its D-domain. However, fibrin clots formed from Hcys-fibrinogen-albumin show a similarly reduced ability to support plasminogen activation and a similar resistance to fibrinolysis as clots formed from Hcys-fibrinogen. Thus, fibrinogen-albumin conjugates may result from N-homocysteinylation of fibrinogen in vivo. However, there is no evidence that conjugation to albumin further impairs fibrinogen function above the defect induced by homocysteinylation of critical lysines. Similar to the utility of glycated hemoglobin as a marker for the deleterious effects of hyperglycemia, the level of fibrinogen-albumin complexes might possibly be a clinically useful marker for the level of homocysteine-associated damage in vivo.
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PMID:Homocysteinylated fibrinogen forms disulfide-linked complexes with albumin. 2131 42