Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that residues Tyr-253 and Glu-255 in the serpin antithrombin function as exosites to promote the inhibition of factor Xa and factor IXa when the serpin is conformationally activated by heparin. Here we show that functional exosites can be engineered at homologous positions in a P1 Arg variant of the serpin alpha1-proteinase inhibitor (alpha1PI) that does not require heparin for activation. The combined effect of the two exosites increased the association rate constant for the reactions of alpha1PI with factors Xa and IXa 11-14-fold, comparable with their rate-enhancing effects on the reactions of heparin-activated antithrombin with these proteases. The effects of the engineered exosites were specific, alpha1PI inhibitor reactions with trypsin and thrombin being unaffected. Mutation of Arg-150 in factor Xa, which interacts with the exosite residues in heparin-activated antithrombin, abrogated the ability of the engineered exosites in alpha1PI to promote factor Xa inhibition. Binding studies showed that the exosites enhance the Michaelis complex interaction of alpha1PI with S195A factor Xa as they do with the heparin-activated antithrombin interaction. Replacement of the P4-P2 AIP reactive loop residues in the alpha1PI exosite variant with a preferred IEG substrate sequence for factor Xa modestly enhanced the reactivity of the exosite mutant inhibitor with factor Xa by approximately 2-fold but greatly increased the selectivity of alpha1PI for inhibiting factor Xa over thrombin by approximately 1000-fold. Together, these results show that a specific and selective inhibitor of factor Xa can be engineered by incorporating factor Xa exosite and reactive site recognition determinants in a serpin.
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PMID:Engineering functional antithrombin exosites in alpha1-proteinase inhibitor that specifically promote the inhibition of factor Xa and factor IXa. 1901 Jul 76

Deep vein thrombosis, the development of blood clots in the peripheral veins, is a very serious, life threatening condition that is prevalent in the elderly. To deliver proper treatment that enhances the survival rate, it is very important to detect thrombi early and at the point of care. We explored the ability of magnetic particle spectroscopy (MSB) to detect thrombus via specific binding of aptamer functionalized magnetic nanoparticles with the blood clot. MSB uses the harmonics produced by nanoparticles in an alternating magnetic field to measure the rotational freedom and, therefore, the bound state of the nanoparticles. The nanoparticles' relaxation time for Brownian rotation increases when bound [A.M. Rauwerdink and J. B. Weaver, Appl. Phys. Lett. 96, 1 (2010)]. The relaxation time can therefore be used to characterize the nanoparticle binding to thrombin in the blood clot. For longer relaxation times, the approach to saturation is more gradual reducing the higher harmonics and the harmonic ratio. The harmonic ratios of nanoparticles conjugated with anti-thrombin aptamers (ATP) decrease significantly over time with blood clot present in the sample medium, compared with nanoparticles without ATP. Moreover, the blood clot removed from the sample medium produced a significant MSB signal, indicating the nanoparticles are immobilized on the clot. Our results show that MSB could be a very useful non-invasive, quick tool to detect blood clots at the point of care so proper treatment can be used to reduce the risks inherent in deep vein thrombosis.
AIP Adv 2017 May
PMID:Blood clot detection using magnetic nanoparticles. 2828 50