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  • Title: A serine proteinase of an archaebacterium, Halobacterium mediterranei. A homologue of eubacterial subtilisins.
    Author: Stepanov VM, Rudenskaya GN, Revina LP, Gryaznova YB, Lysogorskaya EN, Filippova IYu, Ivanova II.
    Journal: Biochem J; 1992 Jul 01; 285 ( Pt 1)(Pt 1):281-6. PubMed ID: 1637313.
    Abstract:
    A homogeneous serine proteinase secreted by the extreme halophilic bacterium Halobacterium mediterranei 1538 was isolated by affinity chromatography on bacitracin-Sepharose with a yield of 48% (260-fold purification). The enzyme reveals an optimum for pyroglutamyl-Ala-Ala-Leu p-nitroanilide hydrolysis at pH 8.0-8.5 (Km 0.14 mM; k(cat). 36.9 s-1). Its activity increases linearly with NaCl concentration over the range 2-5 M. The substrate specificity of the enzyme is comparable with that of secretory subtilisins, the extent of protein degradation approaching that attained with proteinase K. The enzyme has a molecular mass of 41 kDa and a pI of 7.5. The N-terminal sequence of H. mediterranei serine proteinase reveals a 50% identity with that of Thermoactinomyces vulgaris serine proteinases, indicating that the enzyme belongs to the subtilisin family. Hence the serine proteinase secreted by the halophilic bacterium should be considered as a functional analogue, and a structural homologue, of eubacterial serine proteinases (subtilisins).
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