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Main physicochemical features of monofunctional flavokinase from Bacillus subtilis. | LitMetric

Main physicochemical features of monofunctional flavokinase from Bacillus subtilis.

Biochemistry (Mosc)

Department of Molecular and Radiation Biophysics, Konstantinov St. Petersburg Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Leningrad Region, 188350, Russia.

Published: February 2003

The main properties of a monofunctional riboflavin kinase from B. subtilis have been studied for the first time; the enzyme is responsible for a key reaction in flavin biosynthesis--the ATP-dependent phosphorylation of riboflavin with production of flavin mononucleotide. The active form of the enzyme is a monomer with molecular weight of about 26 kD with a strict specificity for reduced riboflavin. To display its maximum activity, the enzyme needs ATP and Mg(2+). During the phosphorylation of riboflavin, Mg(2+) could be partially replaced by ions of other bivalent metals, the efficiencies of which decreased in the series Mg(2+) > Mn(2+) > Zn(2+), whereas Co(2+) and Ca2+ had inhibiting effects. The flavokinase activity was maximal at pH 8.5 and 52 degrees C. ATP could be partially replaced by other triphosphates, their donor activity decreasing in the series: ATP > dATP > CTP > UTP. The Michaelis constants for riboflavin and ATP were 0.15 and 112 micro M, respectively. As compared to riboflavin, a tenfold excess of its analog 7,8-dimethyl-10-(O-methylacetoxime)-isoalloxazine decreased the enzyme activity by 30%. Other analogs of riboflavin failed to markedly affect the enzyme activity.

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http://dx.doi.org/10.1023/a:1022645327972DOI Listing

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