Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cause of death in bacteremia due to Streptococcus pneumoniae remains unclear. The role of intravascular coagulation and splenectomy was investigated in rabbits with lethal pneumococcal bacteremia. The staphylococcal clumping titer in serum, a measure of fibrin degradation products, increased early and persisted until death. This titer correlated with the level of bacteremia. The partial thromboplastin time and platelet-rich plasma clotting time also increased as the disease worsened. However, the prothrombin time remained normal. 125I-labeled fibrinogen was cleared normally from the plasma of infected rabbits, whether intact or splenectomized. Similarly, the concentration of fibrogen in plasma remained normal, even though the level of fibrin degradation products increased, and no difference in these parameters was noted between intact and splenectomized rabbits. Fibrin deposition could not be detected in any of the organs studied. Neither the level of fibrin degradation products nor survival was affected by treatment with hydrocortisone, hexadimethrine, cytochrome c, carboxypeptidase B, epsilon-aminocaproic acid, or heparin. These data suggest that intravascular coagulation occurs in this experimental infection prior to the onset of shock but probably plays only a minor role in lethality.
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PMID:Coagulopathy in experimental sepsis with Streptococcus pneumoniae in rabbits: effect of drug therapy and splenectomy. 97 64

Antistasin (ATS) is a 119-amino acid, leech-derived protein which exhibits selective, tight-binding inhibition of blood coagulation factor Xa. Prolonged incubation of ATS with factor Xa leads to the highly specific hydrolysis of the peptide bond between residues Arg34 and Val35, implicating this peptide bond as the putative reactive site. We report here the preparation of pure, cleaved (modified) recombinant ATS (rATS) and utilize this material to provide additional proof that the cleaved peptide bond is in fact the reactive site. Modified rATS retains strong inhibitory potency against factor Xa as evidenced by a dissociation constant of 166.3 +/- 9.6 pM; four-fold greater than that of native inhibitor, 43.4 +/- 1.4 pM. Incubation of pure, modified rATS with catalytic amounts of factor Xa results in resynthesis of the hydrolyzed peptide bond, achieving an equilibrium near unity between native and modified inhibitors. Specific removal of the newly formed carboxy-terminal Arg residue from modified rATS by carboxypeptidase B treatment obviates its conversion to native inhibitor coincident with the complete loss of inhibitory activity. These results establish that rATS inhibits factor Xa according to a standard mechanism of serine protease inhibitors and support the contention that the Arg34-Val35 peptide bond constitutes the reactive site.
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PMID:The hydrolysis and resynthesis of a single reactive site peptide bond in recombinant antistasin by coagulation factor Xa. 156 19