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    An Antarctic Extreme Halophile and Its Polyextremophilic Enzyme: Effects of Perchlorate Salts

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    Author
    Laye, V.J.
    Dassarma, S.
    Date
    2018
    Journal
    Astrobiology
    Publisher
    Mary Ann Liebert Inc.
    Type
    Article
    
    Metadata
    Show full item record
    See at
    https://dx.doi.org/10.1089/ast.2017.1766
    Abstract
    Effects of perchlorate salts prevalent on the surface of Mars are of significant interest to astrobiology from the perspective of potential life on the Red Planet. Halorubrum lacusprofundi, a cold-adapted halophilic Antarctic archaeon, was able to grow anaerobically on 0.04 M concentration of perchlorate. With increasing concentrations of perchlorate, growth was inhibited, with half-maximal growth rate in ca. 0.3 M NaClO4 and 0.1 M Mg(ClO4)2 under aerobic conditions. Magnesium ions were also inhibitory for growth, but at considerably higher concentrations, with half-maximal growth rate above 1 M. For a purified halophilic ?-galactosidase enzyme of H. lacusprofundi expressed in Halobacterium sp. NRC-1, 50% inhibition of catalytic activity was observed at 0.88 M NaClO4 and 0.13 M Mg(ClO4)2. Magnesium ions were a more potent inhibitor of the enzyme than of cell growth. Steady-state kinetic analysis showed that Mg(ClO4)2 acts as a mixed inhibitor (KI = 0.04 M), with magnesium alone being a competitive inhibitor (KI = 0.3 M) and perchlorate alone acting as a very weak noncompetitive inhibitor (KI = 2 M). Based on the estimated concentrations of perchlorate salts on the surface of Mars, our results show that neither sodium nor magnesium perchlorates would significantly inhibit growth and enzyme activity of halophiles. This is the first study of perchlorate effects on a purified enzyme. � Victoria J. Laye and Shiladitya DasSarma. 2018.
    Sponsors
    We thank Priya DasSarma for assistance with culturing of halophiles. This work was supported by National Aeronautics and Space Administration grant NNX15AM07G.
    Keyword
    Enzyme inhibition
    Halophilic archaea
    Magnesium
    Perchlorate
    Identifier to cite or link to this item
    https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045838301&doi=10.1089%2fast.2017.1766&partnerID=40&md5=8445a0e559c9f9e69b3c4552c4206696; http://hdl.handle.net/10713/8800
    ae974a485f413a2113503eed53cd6c53
    10.1089/ast.2017.1766
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