Structural, Biochemical Characterization and Molecular Mechanism of Cerastokunin: A New Kunitz-Type Peptide with Potential Inhibition of Thrombin, Factor Xa and Platelets.

The current investigation focused on separating Cerastes cerastes venom to produce the first Kunitz-type peptide. Based on its anti-trypsin effect, Cerastokunin, a 7.75 kDa peptide, was purified until homogenity by three steps of chromatography. Cerastokunin was found to include 67 amino acid residues that were obtained by de novo sequencing using LC-MALDI-MSMS. Upon alignment with Kunitz-type peptides, there was a high degree of similarity. Cerastokunin's 3D structure had 12% α-helices and 21% β-strands with pI 8.48. Cerastokunin showed a potent anticoagulant effect by inhibiting the protease activity of thrombin and trypsin as well as blocking the intrinsic and extrinsic coagulation pathways. In both PT and aPPT, Cerastokunin increased the blood clotting time in a dose-dependent way. Using Lys48 and Gln192 for direct binding, Cerastokunin inhibited thrombin, Factor Xa and trypsin as shown by molecular docking. Cerastokunin exhibited a dose-response blockade of PARs-dependent pathway platelet once stimulated by thrombin. An increased concentration of Cerastokunin resulted in a larger decrease of tail thrombus in the mice-carrageenan model in an in vivo investigation when compared to the effects of antithrombotic medications. At all Cerastokunin doses up to 6 mg/kg, no in vivo toxicity was seen in challenged mice over the trial's duration.