Formation of thrombin during incubation of purified bovine prothrombin with purified staphylococcal metalloprotease has been investigated. Thrombin activity was estimated by examination of clotting time and by digestion of a synthetic substrate, Chromozym TH. The metalloprotease caused direct activation of prothrombin which was inhibited by the addition of ethylenediaminetetraacetic acid. Metal...