Kex2 protease, a precursor processing protease derived from yeast, is a calcium-dependent serine protease that specifically recognizes and cleaves the carboxy-terminal peptide bond of the bi-alkaline amino acids Arg-Arg, Lys-Arg, and Pro-Arg. Unlike trypsin, Kex2 does not recognize and cleave the carboxy-terminal peptide bond of a single basic amino acid, arginine or lysine. In yeast, Kex2 protease is responsible for the processing of killer toxin and α-factor precursors. Kex2 protease activity is not inhibited by conventional serine protease inhibitors such as peptidyl peptidase, PMSF and TPCK. The recombinant Kex2 protease is produced by expression of Saccharomyces cerevisiae and has the same enzyme specificity as the natural Saccharomyces cerevisiae Kex2 enzyme. The optimal pH for action is pH 9.0, and the pH for stable storage is pH 5.0-6.0.