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The first crystal structure of human factor Xa was deposited in May 1993. To date, 191 crystal structures of factor Xa with various inhibitors have been deposited in the protein data bank. The active site of factor Xa is divided into four subpockets as S1, S2, S3 and S4. The S1 subpocket determines the major component of selectivity and binding.
Antithrombin (AT) is a small glycoprotein that inactivates several enzymes of the coagulation system. It is a 464-amino-acid protein produced by the liver.It contains three disulfide bonds and a total of four possible glycosylation sites. α-Antithrombin is the dominant form of antithrombin found in blood plasma and has an oligosaccharide occupying each of its four glycosylation sites.
A specialist may request a quantitative factor Xa assay in a situation of overdose. [2] Andexanet alfa, a specific antidote to reverse the anticoagulant activity of direct Xa inhibitors in the event of major bleeding, was approved by the FDA in 2018. [9] It is also available in the UK. [10]
In human adults, the normal blood level of antithrombin activity has been measured to be around 1.1 units/mL. Newborn levels of thrombin steadily increase after birth to reach normal adult levels, from a level of around 0.5 units/mL 1 day after birth, to a level of around 0.9 units/mL after 6 months of life. [12]
The Xa inhibitors all bind in a so-called L-shape fashion within the active site of factor Xa. The key constituents of the factor Xa are the S1 and S4 binding sites. It was first noted that the natural compounds, antistasin and TAP, which possess highly polar and therefore charged components bind to the target with some specificity.
Antithrombin III deficiency (abbreviated ATIII deficiency) is a deficiency of antithrombin III.This deficiency may be inherited or acquired. [1] It is a rare hereditary disorder that generally comes to light when a patient suffers recurrent venous thrombosis and pulmonary embolism, and repetitive intrauterine fetal death (IUFD). [2]
A reference range is usually defined as the set of values 95 percent of the normal population falls within (that is, 95% prediction interval). [2] It is determined by collecting data from vast numbers of laboratory tests.
Results are given in units/mL of anti-factor Xa, such that high values indicate high levels of anticoagulation and low values indicate low levels of anticoagulation in the plasma sample. [ 17 ] LMWHs have a targeted therapeutic window of approximately 0.6–1.2 IU/ml. LMWH has a potency of 70 units/mg of anti-factor Xa activity and a ratio of ...