Selenophosphate synthetase: Enzyme properties and catalytic reaction

Zsuzsa Veres, Ick Young Kim, Thomas D. Scholz, Thressa C. Stadtman

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102 Citations (Scopus)

Abstract

Selenophosphate synthetase, the product of the seID gene, produces the biologically active selenium donor compound, monoselenophosphate, from ATP and selenide. Isolation of the enzyme and characterization of some of its physical and catalytic properties are described. Magnesium ion and a monovalent cation, K+, NH4/+, or Rb+, are required for catalytic activity. Polyphosphates and other common nucleotide triphosphates do not replace ATP as substrate. The stoichiometry of the catalytic reaction (Reaction 1) was established using 31P NMR, anaerobic molecular sieve chromatography, and radiochemical labeling procedures. ATP + selenide + H2O + selenophosphate + P(i) + AMP In the absence of selenide, ATP is converted completely to AMP and orthophosphate upon prolonged incubation with elevated levels of enzyme. AMP is a competitive inhibitor of ATP, K(i) = 170 μM, whereas selenophosphate and orthophosphate are weak inhibitors indicating a multistep reaction. Attempts to obtain direct evidence for a postulated enzyme-pyrophosphate intermediate using several experimental approaches are described. No exchange of [14C]AMP with ATP could be detected after the enzyme was freed of traces of contaminating adenylate kinase by chromatography on phenyl-Sepharose.

Original languageEnglish
Pages (from-to)10597-10603
Number of pages7
JournalJournal of Biological Chemistry
Volume269
Issue number14
Publication statusPublished - 1994 Apr 8

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Veres, Z., Kim, I. Y., Scholz, T. D., & Stadtman, T. C. (1994). Selenophosphate synthetase: Enzyme properties and catalytic reaction. Journal of Biological Chemistry, 269(14), 10597-10603.