Therostasin, a novel clotting factor Xa inhibitor from the rhynchobdellid leech Theromyzon tessulatum

Therostasin is a potent naturally occurring tight-binding inhibitor of mammalian Factor Xa (K(i), 34 pm), isolated from the rhynchobdellid leech Theromyzon tessulatum. Therostasin is a cysteine-rich protein (8991 Da) consisting of 82 amino acid residues with 16 cysteine residues. Its amino acid sequence has been determined by a combination of techniques, including Edman degradation, enzymatic cleavage, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) on the native and s-beta-pyridylethylated compound. Sequence analysis reveals that it shares no significant homology with other Factor Xa inhibitors except for the putative reactive site. Moreover, it contains a signature pattern for proteins of the endothelin family, potent vasoconstrictors isolated in mammal and snake venom. Therostasin cDNA (825 bp) codes for a polypeptide of 82 amino acid residues preceded by 19 residues, representing a signal peptide sequence. As for the other known inhibitors of Factor Xa, therostasin is expressed and stored in the cells of the leech salivary glands.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

Isolates therostasin from Theromyzon tessulatum, a 12-kDa Factor Xa inhibitor — confirms leech Factor Xa inhibitor diversity beyond antistasin.

Leech-derived molecules this paper discusses, each with a full profile in the ASH compound registry:

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