[Characterization of a protease from Thermoactinomyces vulgaris (thermitase). 2. Single-step fine purification and protein-chemical characterization].

The fine purification of an alkaline protease (thermitase) from Thermoactinomyces vulgaris by means of isoelectrical focussing in the flat-bed procedure using granulated gel is reported. An Na2SO4-precipitated crude product serves as the starting material. Isoelectrical focussing leads in a single step to a highly purified protein with an uniform N-terminal end group. The enzyme has an IP at 9.0 and a mol. wt. of 37,400; it consists of a polypeptide chain with arginine as the N-terminal, and tyrosine as the C-terminal end group. In addition to an essential serine residue, a SH group could be demonstrated which is hardly accessible in the native enzyme. Furthermore, the influence of different protease inhibitors was studied.