Separation and comparative characterization of the cationic protease and anionic protease from the culture medium of Thermoactinomyces vulgaris.

The anionic protease component which frequently contaminates preparations of routinely isolated cationic protease (thermitase) from Thermoactinomyces vulgaris was purified, virtually to homogeneity, by rechromatography on controlled pore glass (CPG-10). Starting materials were column eluates with anionic protease, contaminated with residual thermitase activity. The purified anionic enzyme shares several properties with thermitase, such as size, sensitivity against phenylmethanesulfonyl fluoride and Hg2+, UV-spectral, immunological and pH behavior. On the other hand, the isoelectric point (at pH 6.5), temperature dependence (more heat stable) and enzymatic activity (less active) of anionic protease differ significantly from thermitase. At pH 8 or 6 and 25 degrees or 4 degrees C anionic protease is hydrolysed completely by thermitase. Like other protein substrates, anionic protease simultaneously acts as a stabilizer for thermitase. In contrast to thermitase, the anionic enzyme partially changes spontaneously during long-term storage at 4 degrees C and pH 6 to a cationic protein species endowed with proteolytic activity.