Cooperativity of two active sites in bacterial homodimeric aconitases

Daisuke Tsuchiya, Nobutaka Shimizu, Masaru Tomita

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Aconitase catalyzes a reversible isomerization of citrate into isocitrate in the Krebs cycle. Escherichia coli possesses two kinds of aconitases, aconitase A (AcnA) and B (AcnB), whose structural organizations are different. We analyzed the structural state of AcnA by the chemical crosslinking and small-angle X-ray scattering. The protein adopts a homodimer in solution, as AcnB does. The catalytic assay of the two aconitases revealed that the isomerization of isocitrate displayed a negative cooperativity of the two active sites within each homodimer. On the other hand, insignificant cooperativity was observed in the reverse reaction. Therefore, the homodimerization of AcnAB yields a substrate-dependent cooperative effect. In conjunction with the dissociable homodimer of AcnB, the catalytic property could affect the intracellular metabolic process involving the Krebs cycle.

Original languageEnglish
Pages (from-to)485-488
Number of pages4
JournalBiochemical and Biophysical Research Communications
Issue number2
Publication statusPublished - 2009 Feb 6


  • Enzyme catalysis
  • Negative cooperativity
  • Quaternary structure of protein
  • Small-angle X-ray scattering
  • Structural modeling

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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