9000-94-6

 Antithrombin III (CAS NO.9000-94-6) is a small protein molecule that inactivates several enzymes of the coagulation system. It is a glycoprotein produced by the liver and consists of 432 amino acids. 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 single glycosylation site remains consistently un-occupied in the minor form of antithrombin, β-antithrombin.

Antithrombin is a serpin (serine protease inhibitor) and is thus similar in structure to most other plasma protease inhibitors, such as alpha 1-antichymotrypsin, alpha 2-antiplasmin and Heparin cofactor II.
The physiological target proteases of antithrombin are those of the contact activation pathway (formerly known as the intrinsic pathway), namely the activated forms of Factor X (Xa), Factor IX (IXa), Factor XI (XIa), Factor XII (XIIa) and Factor II (thrombin) (IIa) and also the activated form of Factor VII (VIIa) from the tissue factor pathway (formerly known as the extrinsic pathway).The inhibitor also inactivates kallikrein and plasmin, also involved in blood coagulation. However it inactivates certain other serine proteases that are not involved in coagulation such as trypsin and the C1s subunit of the enzyme C1 involved in the classical complement pathway.
Protease inactivation results as a consequence of trapping the protease in an equimolar complex with antithrombin in which the active site of the protease enzyme is inaccessible to its usual substrate.The formation of an antithrombin-protease complex involves an interaction between the protease and a specific reactive peptide bond within antithrombin. In human antithrombin this bond is between arginine (arg) 393 and serine (ser) 394 (see Figure 2 and Figure 3).
It is thought the trapping of protease enzymes in inactive antithrombin-protease complexes results as a consequence of their attack of the reactive bond. Where the attack of a similar bond within their normal substrate results in its rapid proteolytic cleavage, on initiating an attack on the antithrombin reactive bond the antithrombin inhibitor is activated to trap the enzyme at an intermediate stage during the proteolytic process. Given time thrombin is able to cleave the reactive bond within antithrombin and an inactive antithrombin-thrombin complex will dissociate, however the time it takes for this to occur may be greater than 3 days.However bonds P3-P4 and P1'-P2' can be rapidly cleaved by neutrophil elastase and the bacterial enzyme thermolysin respectively, resulting in inactive antithrombins no longer able to inhibit thrombin activity.
The rate of antithrombin's inhibition of protease activity is greatly enhanced by its additional binding to heparin as is its inactivation by neutrophil elastase.

Experimental reproductive effects. When heated to decomposition it emits acrid smoke and irritating vapors.

 Antithrombin III ,its CAS NO. is 9000-94-6,the synonyms is Antraformin ; AT-III ; Atenativ ; BI 6013 ; Heparin cofactor ; Kybernin ; Neuart ; Org 10849 ; Serpin C1 ; Thrombate III ; Thrombin inhibitor ; The glycoprotein antithrombin obtained from human plasma .