Structure-activity relationships of recombinant hirudins
Review published in Seminars in Thrombosis and Hemostasis (1991)
Abstract
The complex formation between thrombin and hirudin is unique among other serine proteinase-inhibitor complexes. The serpines occupy the specificity pocket of the active site of the target enzyme with an amino acid residue corresponding to the specificity of the enzyme at the P1 site of the substrate. In contrast, the Thr2 residue of hirudin approaches only the entrance of the pocket. The peptide chain of the inhibitors D-Phe-Pro-ArgCH2Cl and NAPAP is antiparallel to the enzyme backbone, whereas the N-terminal amino acids of hirudin run parallel. These unexpected interactions seem to contribute to a greater extent to the tight binding than the ionic interactions of the hirudin tail with the fibrinogen binding site of thrombin. Obviously, these interactions account for the unique selectivity of hirudin for thrombin.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Hirudin's Thr2 reaches only the entrance of thrombin's specificity pocket, and its N-terminal chain runs parallel, not antiparallel, to the enzyme backbone. These interactions seem to contribute more to tight binding than the tail's ionic interactions with thrombin's fibrinogen site, accounting for hirudin's selectivity.
Why This Matters for Hirudotherapy
This work examines the molecular interactions in the complex formation between thrombin and hirudin, describing how hirudin's N-terminal amino acids run parallel to the enzyme backbone—in contrast to other serine proteinase-inhibitor complexes—and how the Thr2 residue approaches only the entrance of the specificity pocket. The abstract indicates these interactions contribute more to tight binding than the ionic interactions of the hirudin tail with the fibrinogen binding site of thrombin, accounting for hirudin's unique selectivity for thrombin. Caveat: the scope is limited to biochemical and molecular characterization, with no clinical, whole-organism, or therapeutic application data presented.
Citation
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