Enzymatic characterization of a monomeric isocitrate dehydrogenase from Streptomyces lividans TK54

Beibei Zhang, Baojuan Wang, Peng Wang, Zhengyu Cao, Enqi Huang, Jiasheng Hao, Antony M. Dean, Guoping Zhu

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Isocitrate dehydrogenase (IDH) is one of the key enzymes in the citric acid cycle, which involves in providing energy and biosynthetic precursors for metabolism. Here, we report for the first time the enzymatic characterization of a monomeric NADP+-dependent IDH from Streptomyces lividans TK54 (SlIDH). The icd gene (GenBank database accession number EU661252) encoding IDH was cloned and overexpressed in Escherichia coli. The molecular mass of SlIDH was about 80 kDa, typical of a monomeric NADP-IDH, and showed high amino acid sequence identity with known monomeric IDHs. The optimal activity of the 6His-tagged SlIDH was found at pH values 8.5 (Mn2+) and 9.0 (Mg2+), and the optimal temperature was around 46 °C. Heat-inactivation studies showed that about 50% SlIDH activity was preserved at 38 °C after 20 min of incubation. The recombinant SlIDH displayed a 62,000-fold (kcat/Km) preference for NADP+ over NAD+ with Mn2+, and a 85,000-fold greater specificity for NADP+ than NAD+ with Mg2+. Therefore, SlIDH is a divalent cation-dependent monomeric IDH with remarkably high coenzyme preference for NADP+.

Original languageEnglish (US)
Pages (from-to)1405-1410
Number of pages6
JournalBiochimie
Volume91
Issue number11-12
DOIs
StatePublished - Nov 1 2009

Keywords

  • Coenzyme specificity
  • Kinetics
  • Monomeric isocitrate dehydrogenase
  • Streptomyces lividans
  • Western blot

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