Abstract
We designed a unique anticoagulant decapeptide, which possesses two O-sulfated tyrosine residues, based on the structure of hirudin's C-terminal functional domain. We first prepared a series of octa-, nona- and decapeptides with no sulfation, Suc-Phe-Glu-Pro-Ile-Pro-Glu-Tyr-Tyr-X-OH [X=bond, Leu or Leu-Gln], by a solution phase method and measured their thrombin times (TT) using human thrombin and rabbit plasma. The shortest octapeptide (3a) showed full antithrombin activity compareble to that of the lead compound hirudin (54-65), and the longest decapeptide (3c) prolonged TT most potently with an IC50 value of 5.8 μM. We consequently converted 3c to a disulfated decapeptide (NF-22) with SO3·pyridine complex and compared its antithrombin activity with that of known hirudin-related peptides : hirugen, MDL28050 and hirulog-1. NF-22 showed potent antithrombin activity with an IC50 value of 0.3 μM, being more potent than hirugen and MDL28050 (IC50 values of 4.0 μM and 1.1 μM, respectively). NF-22 was as potent as hirulog-1. NF-22 showed no change in activity in aqueous solution for 10 d at 60°C, and remained about 90% unchanged in rat plasma on incubation for 24 h at 37°C, whereas the corresponding unsulfated peptide (3c) was completely digested under the same condition. NF-22 appears to be one of the most potent and stable peptide anticoagulants among the hirudin analogs.
