Molecular cloning and characterization of NAD+ dependent isocitrate dehydrogenase enzyme from Shewanella putrefaciens

Abstract

Isocitrate dehydrogenase (IDH) is a fundamental enzyme for carbon metabolism in the Krebs cycle. This enzyme is required for oxidation-reduction reactions in both eukaryotic and prokaryotic cells and plays a critical role in their growth and pathogenesis. In this study, we cloned the gene encoding NAD+ dependent isocitrate dehydrogenase from Shewanella putrefaciens. The expression of recombinant protein was induced with 0.5 mM of IPTG. His-tagged IDH overexpressed in E. coli was purified and characterized. The expressed IDH enzyme was purified in an active soluble form. The molecular weight of the enzyme was confirmed with Western blotting. High sequence homology was observed with IDH sequences of other Shewanella strains and remarkable sequence homology was found with other bacteria reported in the database. The open reading frame of the gene encoding IDH of S. putrefaciens was 1069 bp in length, which codes a polypeptide composed of 356 amino acids and with a 38 KDa molecular weight. The optimum enzyme activity was obtained at pH 8. We cloned, purified and characterized Shewanella putrefaciens isocitrate dehydrogenase enzyme (SpIDH). The recombinant enzyme demonstrated a specific activity of Vmax 4.6±0.3 μM/min and Km 334 μM using NAD+ as a cofactor.