Characterization of two β-decarboxylating dehydrogenases from Sulfolobus acidocaldarius

• Published in: Extremophiles : life under extreme conditions 2016-11, Vol.20 (6), p.843-853
• Main Authors: Takahashi, Kento, Nakanishi, Fumika, Tomita, Takeo, Akiyama, Nagisa, Lassak, Kerstin, Albers, Sonja-Verena, Kuzuyama, Tomohisa, Nishiyama, Makoto
• Format: Article
• Language: English
• Subjects: 3-Isopropylmalate Dehydrogenase - genetics; 3-Isopropylmalate Dehydrogenase - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry; Biomedical and Life Sciences; Biotechnology; Escherichia coli; Isocitrate Dehydrogenase - genetics; Isocitrate Dehydrogenase - metabolism; Isocitrates - metabolism; Life Sciences; Magnesium - metabolism; Malates - metabolism; Microbial Ecology; Microbiology; Original Paper; Protein Binding; Space life sciences; Sulfolobus acidocaldarius; Sulfolobus acidocaldarius - enzymology; Sulfolobus acidocaldarius - genetics
• ISSN: 1431-0651; 1433-4909
• DOI: 10.1007/s00792-016-0872-4

Sulfolobus acidocaldarius , a hyperthermoacidophilic archaeon, possesses two β-decarboxylating dehydrogenase genes, saci_0600 and saci_2375 , in its genome, which suggests that it uses these enzymes for three similar reactions in lysine biosynthesis through 2-aminoadipate, leucine biosynthesis, and the tricarboxylic acid cycle. To elucidate their roles, these two genes were expressed in Escherichia coli in the present study and their gene products were characterized. Saci_0600 recognized 3-isopropylmalate as a substrate, but exhibited slight and no activity for homoisocitrate and isocitrate, respectively. Saci_2375 exhibited distinct and similar activities for isocitrate and homoisocitrate, but no detectable activity for 3-isopropylmalate. These results suggest that Saci_0600 is a 3-isopropylmalate dehydrogenase for leucine biosynthesis and Saci_2375 is a dual function enzyme serving as isocitrate-homoisocitrate dehydrogenase. The crystal structure of Saci_0600 was determined as a closed-form complex that binds 3-isopropylmalate and Mg 2+ , thereby revealing the structural basis for the extreme thermostability and novel-type recognition of the 3-isopropyl moiety of the substrate.