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Volume 2 (2006), Issue 1, Pages 51-57
Research Article

Purification and characterization of a thermostable, haloalkaliphilic extracellular serine protease from the extreme halophilic archaeon Halogeometricum borinquense strain TSS101

1Department of Biochemistry, Gulbarga University, Gulbarga-585 106, Karnataka, India
2Department of Environmental Science & Policy, George Mason University, 10900 University Blvd., PW1 MS 4D4, Manassas, Virginia, 20110, USA

Received 6 April 2006; Accepted 23 May 2006

Copyright © 2006 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A novel haloalkaliphilic, thermostable serine protease was purified from the extreme halophilic archaeon, Halogeometricum borinquense strain TSS101. The protease was isolated from a stationary phase culture, purified 116-fold with 18% yield and characterized biochemically. The molecular mass of the purified enzyme was estimated to be 86 kDa. The enzyme showed the highest activity at 60 °C and pH 10.0 in 20% NaCl. The enzyme had high activity over the pH range from 6.0 to 10.0. Enzymatic activity was strongly inhibited by 1 mM phenyl methylsulfonyl fluoride, but activity was increased 59% by 0.1% cetyltrimethylammonium bromide. The enzyme exhibited relatively high thermal stability, retaining 80% of its activity after 1 h at 90 °C. Thermostability increased in the presence of Ca2+. The stability of the enzyme was maintained in 10% sucrose and in the absence of NaCl.