| 10898947 |
Kuhn NJ, Wadeson A, Ward S, Young TW: Methanococcus jannaschii ORF mj0608 codes for a class C inorganic pyrophosphatase protected by Co (2+) or Mn (2+) ions against fluoride inhibition. Arch Biochem Biophys. 2000 Jul 15;379(2):292-8.
Openreading frame mj0608 of the Methanococcus jannaschii genome, recognized by its sequence similarity to that of the gene coding for class C inorganic pyrophosphatase in Bacillus subtilis, was cloned and over-expressed in Escherichia coli. The protein was purified and characterized by SDS-PAGE, M (r), and N-terminal sequence. Under suitable conditions it catalyzed the specific hydrolysis of PPi at about 600 micromol x min (-1) x mg (-1) at 25 degrees C, and at 8000 micromol x min (-1) x mg (-1) at 85 degrees C. Therefore this protein is a specific inorganic pyrophosphatase. The activities of Mg (2+), Mn (2+), Co (2+), and Zn (2+) ions as cofactors for hydrolysis of PPi were compared at pH 7.5 and 9.0. Unlike the class C pyrophosphatase of B. subtilis, this enzyme required no prior activation by low concentrations of Mn (2+) or Co (2+) ions. However, prior exposure to these ions afforded striking protection against inhibition by sodium fluoride, to which the enzyme was otherwise very sensitive. |
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