Ibrahim, Abdelnasser S. S.Abdelnasser S. S.IbrahimAl-Salamah, Ali A.Ali A.Al-SalamahEl-Badawi, Yahya B.Yahya B.El-BadawiEl-Tayeb, Mohamed A.Mohamed A.El-TayebAntranikian, GarabedGarabedAntranikian2020-07-072020-07-072015-07-10Extremophiles 5 (19): 961-971 (2015)http://hdl.handle.net/11420/6632Alkaline protease produced by the halotolerant alkaliphilic Bacillus sp. strain NPST-AK15 was purified to homogeneity by the combination of ammonium sulfate precipitation, anion-exchange and gel permeation chromatography. The purified enzyme was a monomeric protein with an estimated molecular weight of 32 kDa. NPST-AK15 protease was highly active and stable over a wide pH range, with a maximal activity at pH 10.5. The enzyme showed optimum activity at 60 °C and was stable at 30–50 °C for at least 1 h. Thermal stability of the purified protease was substantially improved by CaCl2 (1.1- to 6.6-fold). The Km, Vmax and kcat values for the enzyme were 2.5 mg ml−1, 42.5 µM min−1 mg−1, and 392.46 × 103 min−1, respectively. NPST-AK15 protease activity was strongly inhibited by PMSF, suggesting that the enzyme is a serine protease. The enzyme was highly stable in NaCl up to 20 % (w/v). Moreover, the purified enzyme was stable in several organic solvents such as diethyl ether, benzene, toluene, and chloroform. In addition, it showed high stability and compatibility with a wide range of surfactants and commercial detergents and was slightly activated by hydrogen peroxide. These features of NPST-AK15 protease make this enzyme a promising candidate for application in the laundry and pharmaceutical industries.en1433-490920155961971Springeralkaline proteasealkaliphilesbacillus spdetergent stablepurificationsolvent stableBiowissenschaften, BiologieJournal Article10.1007/s00792-015-0771-0Other