Kinetic pathway for the slow to fast transition of thrombin. Evidence of linked ligand binding at structurally distinct domains.
Research article published in The Journal of biological chemistry (1997)
Abstract
The kinetic pathway for the Na+-induced slow --> fast transition of thrombin was characterized. The slow form was shown to consist of two conformers in a 3:1 ratio (ES2:ES1) at 5 degrees C, pH 7.4, Gamma/2 0.3. ES2 binds Na+ 3 orders of magnitude faster than does ES1. The small molecule active site-directed inhibitor L-371,912, and the exosite I binding ligand hirugen, like Na+, bind selectively to ES2 and induce the slow --> fast conversion of thrombin. The slow --> fast transition is limited by the rate of conversion of ES1 to ES2 (k approximately 28 s-1 at 5 degrees C). Replacement of Arg-221a or Lys-224 at the Na+ binding site with Ala appears to selectively alter the slow form and reduce the apparent affinity of the mutants for Na+ and L-371,912. This replacement, however, has little effect on the affinity for the inhibitor in the presence of saturating concentrations of Na+. The kinetically linked ligand binding at the Na+ binding site, exosite I, and the active site of thrombin characterized in the present study indicates the basis for the plasticity of this important enzyme, and suggests the possibility that the substrate specificity and, therefore, the procoagulant and anticoagulant activities of thrombin may be subject to allosteric regulation by as yet unidentified physiologically important effectors.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Resumen
The kinetic pathway for the Na+-induced slow --> fast transition of thrombin was characterized. The slow form was shown to consist of two conformers in a 3:1 ratio (ES2:ES1) at 5 degrees C, pH 7.4, Gamma/2 0.3.
Por qué esto importa para la hirudoterapia
El resumen caracteriza la vía cinética de la transición lenta-a-rápida de la trombina inducida por Na+, identifica dos confórmeros de forma lenta y demuestra que el inhibidor dirigido al sitio activo L-371,912 y el ligando de unión al exositio I hirugen se unen cada uno de manera selectiva a un confórmero e inducen la conversión de lenta a rápida. Las mutaciones en Arg-221a o Lys-224 alteran la forma lenta y reducen la afinidad aparente por el Na+ y por L-371,912. El único posible vínculo con el dominio de la ASH en el resumen es el ligando nombrado 'hirugen', pero el resumen no señala que sea derivado de sanguijuela, derivado de hirudina, ni relacionado con la hirudoterapia. Así, ninguna relevancia directa con la sanguijuela o la hirudoterapia queda establecida por el propio resumen; la relevancia se limita al alosterismo de la trombina y a la cinética de unión al ligando.
Citación
Kinetic pathway for the slow to fast transition of thrombin. Evidence of linked ligand binding at structurally distinct domains.
Lai et al. · The Journal of biological chemistry, 1997
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Añadido a la biblioteca ASH: May 28, 2026 · Última actualización del sitio: 18 de junio de 2026