Inhibition of bovine and human thrombins by derivatives of benzamidine.

Thirty-four derivatives of benzamidine were tested for their inhibitory activities on bovine and human thrombins using the chromogenic peptide substrate N-D-Phe-Pip-Arg-pNA. The inhibition constants of small molecular size inhibitors of comparatively low affinity as well as those of tight binding inhibitors did not differ significantly with different species. Accordingly, the active site of bovine thrombin seems to correspond largely to that of human thrombin.