Anticoagulant from Taraxacum platycarpum.

An anticoagulant was purified from a Chinese herb, Taraxacum platycarpum. Its activity was heat-labile, and was decreased by incubation with subtilisin Carlburg or proteinase K, indicating that the active component was a protein. The protein had a molecular mass of 31 kDa by gel filtration and 33 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, so it probably was a monomer. When present at the concentration of 70, 255, and 873 nM, respectively, the protein doubled the thrombin time, prothrombin time, and activated partial thromboplastin time. It inhibited thrombin and kallikrein, but did not hydrolyze fibrinogen. The protein bound the anion-binding exosite of thrombin, competing with the fibrinogen binding site. In addition, the protein caused the murine macrophage cell line Raw 264.7 to produce cyclooxygenase-2, nitric oxide synthase, nitric oxide, and tumor necrosis factor-alpha.