Serine proteases thrombin

Fibrin is formed from fibrinogen synthesized by the liver and secreted into the circulation. The conversion of fibrinogen to fibrin is initiated by a serine protease, thrombin. Thrombin, at the same time, can activate a transglutaminase enzyme, factor XIII present in... 

Sheehan JJ, Tsirka SE. Fibrin-modifying serine proteases thrombin, tPA, and plasmin in ischemic stroke a review. Glia 2005 50(4) 340-50. 

Hie serine protease thrombin takes a central position in the clotting system. It splits off fibrinopeptides A and B from the amino terminal ends of the a- and -chains of fibrinogen. The resulting fibrin monomer then undergoes polymerization to forma fibrin dot. Via activation of the clotting factors V and VIII, further thrombin is Generated from wothramhin. and via activation of blood dale lets and... 

Many pharmaceutical companies are actively working on the development of orally active inhibitors of the serine protease thrombin as one important enzyme in the blood coagulation cascade. In many cases, however, the systemic exposure to thrombin inhibitors... 

An example of the method has been published [ 14] that compares studies on three closely related serine proteases thrombin, factor Xa and trypsin. 4-point multiple potential pharmacophore keys were generated from site-points positioned in the active sites using the results of GRID analyses. These are illustrated in figure 10, together with the number of overlapping... 

Figure 3.5. Typical example of a CPCA score plot, here for the serine proteases thrombin, trypsin, and factor Xa. Each point in the plot represents one input protein structure. The different structures for each protein are clustered. PC 1 discriminates thrombin and trypsin, PC 2 distinguishes factor Xa from thrombin and trypsin.

Kastenholz et al. published the first application of the CPCA method. It dealt with the three serine proteases thrombin, factor Xa, and trypsin [8]. The score plot of the analysis which employed a total of 13 X-ray structures is shown in Fig. 3.5. PC 1 distinguishes between the thrombin and trypsin structures, while PC 2 separates factor Xa from the remaining two enzymes. The usual ligand binding region, which is very similar in all three enzymes, can be subdivided into three subpockets SI, P and D [36] (see Fig. 3.8). With the cut-out tool, each of the three sub-pockets was investigated separately. 

Protease substrates (serine protease thrombin, cysteine protease caspase-3)... 

Pharmacophore fingerprints generated from complementary site points can be used to direct combinatorial library design and to investigate selectivity. An example of the pharmacophore fingerprinting method for selectivity studies has been validated (37a,b) in studies of three closely related serine proteases thrombin, Factor Xa, and trypsin. Site points were... 

Viperidae endopeptidase, factor X activator, fibrinogenase, kininogenase, metalloproteinase, prothrombin activator, serine protease, thrombin-like enzyme... 

Prothrombin is the precursor of the serine protease thrombin, essential for normal haemostasis in activation of platelets and in catalysing the polymerisation of fibrinogen to fibrin. It is synthesized in the liver and contains about 8% total carbohydrate in four N-glycans. Three of these lie on the Pro region and only one is present on the mature a-thrombin molecule. The structure of the thrombin glycan has been determined by mass spectrometry and is the same as that shown in Fig. 5 A with fucose absent or present [77]. 

Prothrombin, thromhogen, factor II, the zymogen of the serine protease thrombin. Prothrombin occurs in all vertebrates, and is activated after initiation of the coagulation cascade at the site of vascular injury. Prothrombin consists of the thrombin domain, a Gla domain, and two kringle domains [J. Stenflo et al., Proc. Natl. Acad. Sci. USA 1974, 72, 2730 K. G. Mann et al.. Methods Enzymol. 1981, 80, 286]. 

One of the most widely-studied group of aptamers are those binding to the serine protease thrombin found in blood serum, and there are again many reports of thrombin aptamers during this review period. NMR studies of the aptamer sequence (G2T2G2TGTG2T2G2) showed a well-defined antiparallel unimolecular species in the presence of NH4" " or K+ ions, but... 

Heparin has been fluorescently labeUed in a manner that does not alter the functional properties of the polysaccharide. The labelled polysaccharide has been used in conjunction with fluorescence polarization spectroscopy to monitor the binding of heparin to the L-serine proteases thrombin, factor XIa, factor Xa, and plasmin. The stoicheiometry and dissociation constants of the interactions have been measured. The kinetics of inactivation of the four proteases by anti-thrombin as a function of heparin concentration have also been measured. Evidence shows that the direct binding of heparin to anti-thrombin is probably responsible for the polysaccharide-dependent acceleration of hemostatic enzyme-inhibitor reactions. 

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