Designing allosteric regulators of thrombin. Exosite 2 features multiple subsites that can be targeted by sulfated small molecules for inducing inhibition.
Research article published in Journal of medicinal chemistry (2013)
Abstract
We recently designed a group of novel exosite-2-directed sulfated, small, allosteric inhibitors of thrombin. To develop more potent inhibitors, monosulfated benzofuran tri- and tetrameric homologues of the parent designed dimers were synthesized in seven to eight steps and found to exhibit a wide range of potencies. Among these, trimer 9a was found to be nearly 10-fold more potent than the first generation molecules. Michaelis-Menten studies indicated an allosteric mechanism of inhibition. Competitive studies using a hirudin peptide (exosite 1 ligand) and unfractionated heparin, heparin octasaccharide, and γ'-fibrinogen peptide (exosite 2 ligands) demonstrated exosite 2 recognition in a manner different from that of the parent dimers. Alanine scanning mutagenesis of 12 Arg/Lys residues of exosite 2 revealed a defect in 9a potency for Arg233Ala thrombin only confirming the major difference in site of recognition between the two structurally related sulfated benzofurans. The results suggest that multiple avenues are available within exosite 2 for inducing thrombin inhibition.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
We recently designed a group of novel exosite-2-directed sulfated, small, allosteric inhibitors of thrombin. To develop more potent inhibitors, monosulfated benzofuran tri- and tetrameric homologues of the parent designed dimers were synthesized in seven to eight steps and found to exhibit a wide range of potencies.
Why This Matters for Hirudotherapy
This drug-design study synthesized sulfated benzofuran small molecules aimed at thrombin's exosite 2 and identified a trimer (9a) roughly tenfold more potent than earlier dimers, with Michaelis-Menten and alanine-scanning data supporting an allosteric mechanism and a distinct exosite-2 recognition site (a potency defect at Arg233). It connects to hirudotherapy through its experimental use of a hirudin peptide as an exosite-1 ligand in competition studies, illustrating how the leech anticoagulant hirudin serves as a molecular tool and reference point in modern thrombin-inhibitor research. This is in-vitro medicinal chemistry on synthetic compounds, not a study of leech therapy or a clinical investigation, so its relevance to ASH is mechanistic and contextual rather than evidence of therapeutic benefit.
Citation
Designing allosteric regulators of thrombin. Exosite 2 features multiple subsites that can be targeted by sulfated small molecules for inducing inhibition.
Sidhu PS et al. · Journal of medicinal chemistry, 2013
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