properties of matter : from Clostridium histolyticum. Chromatographically purified. It isis a two chain proteinase associated with collagenase and isolated from Clostridium histolyticum. It is highly specific for the carboxyl peptide bond of arginine. Clostripain has a sulfhydryl requirement; it is activated by dithiothreitol, cysteine, or other sulfhydryl containing reagents. The presence of calcium ions is essential. The enzyme is inhibited by oxidizing agents and sulfhydryl reactants and by Co2+, Cu2+, Cd2+, and heavy metal ions. Citrate, borate, and Tris anions are less inhibitory. One/Unit hydrolyzes one micromole of N-benzoyl-L-arginine ethyl ester per minute at 25°C, pH 7.6, in the presence of dithiothreitol.