An antimicrobial oxidative- and SDS-stable fibrinolytic alkaline protease designated as KSK-II was produced by Lactobacillus plantarum KSK-II isolated from kishk, a traditional Egyptian food. Maximum enzyme productivity was obtained in medium containing 1% lactose and 0.5% soybean flour as carbon and nitrogen sources, respectively. Purification of enzyme increased its specific activity to 1,140-fold with a recovery of 33% and molecular weight of 43.6 kDa. Enzyme activity was totally lost in the presence of ethylenediaminetetraacetic acid and was restored after addition of Fe2+ suggesting that KSK-II is a metalloprotease and Fe2+ acts as cofactor. Enzyme hydrolyzed not only the natural proteins but also synthetic substrates, particularly Suc-Ala-Ala-Pro-Phe-pNA. KSK-II can hydrolyze the Lys-X easier than Arg-X; thus, it was considered as a subtilisin-family protease. Its apparent K-m, V-max, and K-cat were 0.41 mM, 6.4 mu mol mg(-1) min(-1), and 28.0 s(-1), respectively. KSK-II is industrially important from the perspectives of its maximal activity at 50 degrees C (stable up to 70 degrees C), ability to function at alkaline pH (10.0), stability at broad pH ranges (7.5-12.0) in addition to its stability toward SDS, H2O2, organic solvents, and detergents. We emphasize for the first time the potential of fibrinolytic activity for alkaline proteases used in detergents especially in blood destaining. (c) 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:316-324, 2015