Thrombin hirudin

Grtitter, M.G., et al. Crystal structure of the thrombin-hirudin complex a novel mode of serine protease inhibition. EMBO J. 9 2361-2365, 1990. 

Collectively, the direct thrombin inhibitors are prototypically represented by hirudin, the antithrombotic molecule found in the saliva of the medicinal leech (Hirudo medicinalis), This protein is a 65 amino acid molecule that forms a highly stable but noncovalent complex with thrombin (7). With two domains, the NH2-terminal core domain and the COOH-terminal tail, the hirudin molecule inhibits the catalytic site and the anion-binding exosite in a two-step process. The first step is an ionic interaction that leads to a rearrangement of the thrombin-hirudin complex to form a tighter bond that is stoi-chiometrically I I and irreversible. The apolar-binding site may also be involved in hirudin binding. This complex and... 

Karshikov A, Bode W, Tulinsky A, et al. (1992). Electrostatic interactions in the association of proteins An analysis of the thrombin-hirudin complex. Protein Sci. 1 727-735. 

Hirudin is a polypeptide derived from the saliva of the leech Hirudo medicinalis that binds to the blood serine proteinase, thrombins, and thus blocks clot formation. 

The most potent thrombin inhibitor is hirudin, originally isolated from the salivary glands of the medicinal leech Hirudo medicinalis. Its inhibition constant is in the femtomolar (10-15 M) range (57). It is a 65-amino-acid tyrosine-sulfated single-chain polypeptide. Recombinant hirudin differs from native hirudin by the absence of the sulfate group on tyrosine 63 (Tyr-63) and is referred to as desulfato hirudin. The loss of this sulfate group reduces the thrombin inhibitory potency by 10-fold. 

Bivalent inhibitors of thrombin have been synthesized to bind the anion-binding exosite and active (catalytic) site of thrombin simultaneously. By coupling the carboxy terminal fragment of hirudin to a tripeptide (D-Phe-Pro-Arg) by including a spacer molecule, both the anion exosite and the catalytic site are blocked. An example of such a molecule is Hirulog, which has 20 amino acids and has a Kj of 2 nM (61). Its ability to block the active site has been questioned, since thrombin has been shown to cleave the Arg-Pro bond of Hirulog slowly in vivo (58). In addition to hirudin and hirudin-like compounds, three other classes of site-directed thrombin inhibitors deserve mention. 

Direct thrombin inhibitors such as hirudin, Hirulog, the peptide aldehyde efegatran, and peptidomimetic compound argatroban have undergone clinical trials. Their application in the prevention and treatment of deep vein thrombosis contin-... 

Finally, with the use of direct thrombin inhibitors such as hirudin for anticoagulant therapy, laboratory tests such as APTT may not be sensitive enough to follow therapy. 

Rydel T. J., Ravichandran K. G., Tulinsky A., et al. The structure of a complex of recombinant hirudin and human alpha-thrombin. Science 1990 249,277-80. 

Eriksson B. I., Ekmann S. T Kalebo P., et al. Prevention of deep-vein thrombosis after total hip replacement Direct thrombin inhibition with recombinant hirudin, CCG 39393. Lancet 1996 347,635-9. 

Hirudin is a leech-derived anticoagulant that functions by directly inhibiting thrombin. A range of blood-sucking animals contain substances in their saliva that specifically inhibit some element of the blood coagulation system (Table 12.4). 

Hirudin exhibits its anticoagulant effect by tightly binding thrombin, thus inactivating it. In addition to its critical role in the production of a fibrin clot, thrombin displays several other (non-enzymatic) biological activities important in sustaining haemostasis. These include ... 

Hirudin 7 000 Hirudo medicinalis Binds to and inhibits thrombin... 

Figure 12.8 Binding of hirudin to thrombin, thus inactivating this activated coagulation factor...

Stimulation by thrombin does not lead to the generation of leukotriene C4 or B4, whereas stimulation of the same mast cells by the calcium ionophore, A23187, does. The secretory response elicited by thrombin is prevented by preincubation with AT-III, a plasma inhibitor of thrombin, or by hirudin, a thrombin inhibitor derived from the leech [135],... 

De Filippis, V., DeBoni, S., DeDea, E., Dalzoppo, D., Grandi, C., and Fontana, A. Incorporation of the fluorescent amino acid 7-azatryptophan into the core domain 1-47 of hirudin as a probe of hirudin folding and thrombin recognition, Protein Sci., 13 1489-1502,2004. 

Bivalirudin (55 Angiomax ) Hirudin Peptide Synthetic congener Animal Antittirombotic Specific and reversible direct thrombin inhibitor (DTI) 479 91... 

Pharmacology Lepirudin (rDNA), a recombinant hirudin derived from yeast cells, is a highly specific direct inhibitor of thrombin. 

Fitzgerald, G. (1996). The human pharmacology of thrombin inhibition. Coronary Artery Dis. 7(12), 911-918. Markwardt, F. (1991). Hirudin and its derivatives as anticoagulant agents. Thromb. Haemost. 66, 141-152. 

In contrast direct-acting preparations have the ability to inhibit fibrin-bound thrombin and include hirudin derived from medicinal leeches but now produced by recombinant technology. Particular interest centres on ximelagatran which may be a possible... 

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