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a soluble protein, a globulin, in blood plasma, converted to fibrin by the action of the enzyme thrombin when blood clots


The major clot-forming substrate in the blood plasma of vertebrates. Though fibrinogen represents a small fraction of plasma proteins (normal human plasma has a fibrinogen content of 2–4 mg/ml of a total of 70 mg protein/ml), its conversion to fibrin causes a gelation which blocks the flow of blood. Upon injury, sufficient amounts of the clotting enzyme, thrombin, are generated in about 5 min clotting time to produce a gel. Although clotting in the circulation (thrombosis) can be extremely dangerous, clotting is an essential and normal response for preventing the loss of blood. Individuals born with the hereditary absence of fibrinogen (afibrinogenemia) suffer from severe bleeding, which can be counteracted by transfusing normal plasma or purified fibrinogen.

Fibrinogen is synthesized by the hepatocytes in the liver, and the synthetic rate can be stimulated by hormones. Significant amounts of carbohydrates become attached to the protein before it is secreted into the circulation; alterations in its carbohydrate composition as found in some liver diseases can give rise to abnormal fibrinogens with defective clotting properties.

Clotting is regulated by two enzymes, thrombin and factor XIIIa (fibrinoligase, activated fibrin-stabilizing factor, transglutaminase). Thrombin exerts a dual control by regulating the rate of fibrin formation as well as producing factor XIIIa. In the plasma milieu, the fibrin molecules readily aggregate into a clot. In order to obtain a clot structure of a strength sufficient to stem bleeding, however, it is necessary for the thrombin-modified factor XIII to be activated to XIIIa. Factor XIIIa acts as a transamidating enzyme which strengthens the fibrin clot by creating cross-links between the molecules. Without such cross-links, a clot structure would be like a brick wall without mortar. Individuals with the hereditary absence of factor XIII often suffer from severe bleeding, even though their clotting times are in the normal range. See Blood, Immunoglobulin



a soluble plasma protein belonging to the globulin class; coagulation factor I, which is converted to fibrin by the action of the enzyme thrombin. Molecular weight, approximately 350,000.

The fibrinogen molecule is globular, with a diameter of about 22 nanometers. It consists of two identical subunits, each of which is formed of three dissimilar polypeptide chains designated α, β, and γ, where α and β are peptides split off by the action of thrombin. Fibrinogen is synthesized in the parenchymatous cells of the liver. Its concentration in human plasma is 300–500 mg per 100 milliliters. A hemorrhagic diathesis occurs as a result of fibrinogen insufficiency or the formation of molecules with an anomalous structure.

Fibrinogen obtained by precipitation with ethyl alcohol from plasma is used to arrest bleeding during surgery, in obstetrical and gynecological practice, and in cases of hemophilia and diseases associated with low blood fibrinogen levels. Fibrinogen preparations are also produced for laboratory research. Fibrinogen derived from human blood is used clinically.


Andreenko, G. V. “Sovremennye dannye o khimii i fiziologii fibrinogena.” Uspekhi sovremennoi biologii, 1974, vol. 77, issue 1.
“Models Proposed for the Fibrinogen Molecule and for the Polymerization Process.” Thrombosis Research, 1975, vol. 6.



A plasma protein synthesized by the parenchymal cells of the liver; the precursor of fibrin. Also known as factor I.
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Researchers can now look for new ways to target fibrinogen as a way to restore regenerative functions in the central nervous system.
Shandong Taibang is expected to receive the good manufacturing practice certificate from the CFDA within a month and commence commercial production immediately thereafter and expects the first batch of fibrinogen products to be released to market by the end of 2017.
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Upon admission, serum levels of CRP, fibrinogen, N-terminal of the pro-hormone brain natriuretic peptide (NT-proBNP) and WBC count were measured.
The following tests of haemostasis are done only once: Platelet count and peripheral smear, PT (Prothrombin time), aPTT (activated Partial Thromboplastin Time), Fibrinogen and D-dimer.
A plasma fibrinogen concentration <100 mg/dL had been previously considered to be a suitable threshold to initiate its replacement, which is often done by transfusion of fresh frozen plasma (FFP) that has an approximate fibrinogen concentration of 200mg/dL or cryoprecipitate which can reach up to 400 mg per unit.
The report provides a snapshot of the global therapeutic landscape of Fibrinogen Deficiency (Factor I Deficiency)
Therefore, we hypothesized that there is some association between baseline elevated fibrinogen or lowered HDL-C levels, or both in combination, with the recurrence of CVT.
The patient who presented to the Pediatric Hematology Outpatient clinic because of unstoppable gingival bleeding for the first time in 2006 was diagnosed with congenital afibrinogenemia with findings including a prothrombin time (>120 s) and an activated partial thromboplastin time (>120 s) which were too long to be measured and a fibrinogen level which was too low to be measured.
In contrast to winter swimmers, after two months of cryotherapy plasma concentration of fibrinogen was significantly higher than prior to the experiment.
We reviewed the records of all patients and recorded the following details: age of onset, genotypes of FMF gene mutations, clinical features (fever and abdominal, thoracic, articular, skin, muscular, testicular, and miscellaneous manifestations), and laboratory parameters including erythrocyte sedimentation rate (ESR), CRP, fibrinogen, and white blood cell count during attack-free periods.
Further tests indicated that this fibrinogen cleaving inhibited fungal infection in the mice, says study coauthor David Corry, an immunologist and pulmonologist at Baylor College of Medicine in Houston.

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