Allosteric modulation of BPTI interaction with human alpha- and zeta-thrombin.
Research article published in European journal of biochemistry (1999)
Abstract
In this study, thrombin interaction with the basic pancreatic trypsin inhibitor (BPTI) was investigated in the presence of different allosteric modulators of thrombin, that is the C-terminal hirudin peptide 54-65 (Hir54-65), a recombinant thrombomodulin form (TMEGF4-6) and Na+. BPTI binding to alpha-thrombin is positively linked to Na+. Under low sodium concentration (5 mM Na+) the BPTI affinity for alpha-thrombin was roughly threefold lower than in the presence of 150 mM sodium (Ki = 320 microM vs. 100 microM). The hirudin fragment, which binds to the fibrinogen recognition site (FRS) of thrombin, induced a progressive and saturable decrease (3.6-fold) of alpha-thrombin affinity for BPTI, whereas the thrombomodulin peptide, which binds to a more extended region of FRS, caused a 5.5-fold increase of the enzyme affinity for the inhibitor. The opposite effect exerted by Hir54-65 and TMEGF4-6 was also observed for BPTI interaction with zeta-thrombin, in which the amidic bond between W148 and T149 is cleaved. However, in this case the effect by Hir54-65 and TMEGF4-6, although qualitatively similar to that observed with alpha-thrombin, had a smaller magnitude. Thrombin hydrolysis of Protein C was also differently affected by Hir54-65 and TMEGF4-6 peptides. While the latter enhanced the Protein C activation, the former caused a reduction of both alpha- and zeta-thrombin kcat/K(m)' for Protein C cleavage. These results showed that (a) Na+ facilitates BPTI interaction with thrombin; (b) Hir54-65 and TMEGF4-6, though sharing in part the same binding site at the thrombin FRS, can affect in opposite way thrombin's interaction with BPTI and Protein C; (c) such findings along with the results obtained with zeta-thrombin might be explained by admitting that the thermodynamic linkage between FRS and the critical W60-loop is also controlled by ligation and/or conformational state of the W148 insertion loop.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Resumen
In this study, thrombin interaction with the basic pancreatic trypsin inhibitor (BPTI) was investigated in the presence of different allosteric modulators of thrombin, that is the C-terminal hirudin peptide 54-65 (Hir54-65), a recombinant thrombomodulin form (TMEGF4-6) and Na+. BPTI binding to...
Por qué esto importa para la hirudoterapia
Este estudio cinético in vitro investigó cómo los moduladores alostéricos —incluidos el péptido C-terminal de hirudina Hir54-65, un fragmento recombinante de trombomodulina (TMEGF4-6) y Na+— influyen en la unión del BPTI a la alfa- y zeta-trombina humana. El fragmento de hirudina, que se une al sitio de reconocimiento del fibrinógeno de la trombina, redujo la afinidad de la alfa-trombina por el BPTI 3,6 veces, mientras que TMEGF4-6 la aumentó 5,5 veces; ambos también modularon de forma opuesta la activación de la proteína C. Este estudio es directamente relevante para la investigación en hirudoterapia porque caracteriza la interacción molecular de un péptido definido derivado de la hirudina con la trombina, avanzando en la comprensión de cómo los componentes del secretoma de la sanguijuela regulan alostéricamente esta proteasa clave de la coagulación. La advertencia es que el trabajo es puramente bioquímico/in vitro, emplea un fragmento sintético de hirudina en lugar de hirudina completa o secreción cruda de sanguijuela, y no aborda la aplicación terapéutica de la hirudoterapia in vivo.
Citación
Allosteric modulation of BPTI interaction with human alpha- and zeta-thrombin.
De Cristofaro et al. · European journal of biochemistry, 1999
Contexto clínico relacionado
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Añadido a la biblioteca ASH: May 28, 2026 · Última actualización del sitio: June 18, 2026