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Extremophiles. 2016 Nov;20(6):843-853. Epub 2016 Sep 2.

Characterization of two β-decarboxylating dehydrogenases from Sulfolobus acidocaldarius.

Author information

1
Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
2
Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
3
Molecular Biology of Archaea, Institute of Biology II, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany.
4
Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. umanis@mail.ecc.u-tokyo.ac.jp.

Abstract

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 Mg2+, thereby revealing the structural basis for the extreme thermostability and novel-type recognition of the 3-isopropyl moiety of the substrate.

KEYWORDS:

3-Isopropylmalate dehydrogenase; Crystal structure; Homoisocitrate dehydrogenase; Isocitrate dehydrogenase; Sulfolobus acidocaldarius; β-Decarboxylating dehydrogenase

PMID:
27590116
DOI:
10.1007/s00792-016-0872-4
[Indexed for MEDLINE]

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