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. © 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
Inoue, H., Tamura, T., Ehara, N., Nishito, A., Nakayama, Y., Maekawa, M., … Inagaki, K. (2002). Biochemical and molecular characterization of the NAD+-dependent isocitrate dehydrogenase from the chemolithotroph Acidithiobacillus thiooxidans. FEMS Microbiology Letters, 214(1), 127–132. https://doi.org/10.1016/S0378-1097(02)00857-1