Biochemical and molecular characterization of the NAD+-dependent isocitrate dehydrogenase from the chemolithotroph Acidithiobacillus thiooxidans

Hiroyuki Inoue, Takashi Tamura, Nagisa Ehara, Akira Nishito, Yumi Nakayama, Makiko Maekawa, Katsumi Imada, Hidehiko Tanaka, Kenji Inagaki

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


An isocitrate dehydrogenase (ICDH) with an unique coenzyme specificity from Acidithiobacillus thiooxidans was purified and characterized, and its gene was cloned. The native enzyme was homodimeric with a subunit of Mr 45 000 and showed a 78-fold preference for NAD+ over NADP+. The cloned ICDH gene (icd) was expressed in an icd-deficient strain of Escherichia coli EB106; the activity was found in the cell extract. The gene encodes a 429-amino acid polypeptide and is located between open reading frames encoding a putative aconitase gene (upstream of icd) and a putative succinyl-CoA synthase β-subunit gene (downstream of icd). A. thiooxidans ICDH showed high sequence similarity to bacterial NADP+-dependent ICDH rather than eukaryotic NAD+-dependent ICDH, but the NAD+-preference of the enzyme was suggested due to residues conserved in the coenzyme binding site of the NAD+-dependent decarboxylating dehydrogenase.

Original languageEnglish
Pages (from-to)127-132
Number of pages6
JournalFEMS Microbiology Letters
Issue number1
Publication statusPublished - Aug 27 2002


  • Acidithiobacillus thiooxidans
  • Coenzyme specificity
  • Decarboxylating dehydrogenase
  • Enzyme purification
  • Isocitrate dehydrogenase

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology
  • Genetics


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