Accelerator globulin factor

Proaccelerin Accelerator Globulin (Ac-G) V Factor V deficiency, (parahemophilia) Increased risk for thrombosis (Factor V Leiden) Extremely rare 7-10 0.025 Liver, megakaryocytes, endothelial cells 11-15 FA5 HUMAN... 

The antihemophilic globulin, the factor absent from the blood in the best-known hemophilia, combines stoichiometrically with a platelet thromboplastic factor, and the two compounds act like precursors, yielding a product itself a precursor. For thromboplastin, the product is prothromboplastin. The platelet thromboplastin component acts like a catalyst consequently, its concentration does not change during the reaction. The prothromboplastin combines with another compound called the plasma-accelerating globulin to yield a new product, namely, thromboplastin. 

Deficiencies in other factors, such as the plasma thromboplastin antecedent, the accelerator globulin, and the serum prothrombin conversion factor have all been described. The deficiencies lead to various forms of hemophilia. The severity of degree of bleeding episodes is much less marked than in classical hemophilia. These deficiencies are usually congenital, transmitted by sex-linked dominant or recessive or by autosomal dominant genes. The manifestations of these deficiencies are usually referred to as hemophilioid states c, d, a, and b, respectively. The major characteristics of these various types of congenital hemophilioid states are summarized in Table 7-4. 

Deficiencies in the accelerated globulin and the serum prothrombin conversion factor may be acquired. The accelerated globulin deficiency occurs in severe hepatic disease, acute leukemia, postoperative states, radiation injury, after isotope administration, and in late stages of cancer. Deficiencies of the serum thrombin conversion factors also occur in advanced liver disease, but they develop as well when anticoagulants are administered. 

Proconvertin, serum prothrombin conversion accelerator (SPCA), cothromboplastin Antihemophilic factor A, antihemophilic globulin (AHG)... 

In the last several years, it has become known and more appreciated that the in vivo role of heparin as an anticoagulant may be less important as an inhibitor of thrombin and more important as an inhibitor of Factor Xa.8B Actually heparin is not an anticoagulant, but a cofactor for a protein (a8 globulin - antithrombin III) in the plasma that neutralizes Factor Xa or thrombin by molecular combination. Without heparin this neutralization, which is concentration dependent, is slow. In the presence of heparin, it is greatly accelerated. Heparin has no effect on thrombin... 

The next series of transformations leads to thrombin formation. A precursor of thrombin, the familiar prothrombin whose synthesis in the liver requires vitamin K, combines with thromboplastin stoichiometrically. The reaction requires calcium and a platelet factor referred to as platelet factor 1. The product of the reaction is thrombin but prothrombin production by the mechanism just described is so slow that the process must be activated for efficient coagulation, and thrombin catalyzes its own production. Thus, thrombin converts a plasma component, factor 1, or the plasma AC globulin into an active catalyst capable of accelerating prothrombin conversion to thrombin. 

Ac-globulin thrombogen factor V labile factor component A of prothrombin prothrombin accelerator proacce-lerin accelerator factor plasma prothrombin conversion factor plasmatic cofactor of thromboplastin prothrom-binase... 

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