title: Molecular and phylogenetic characterization of isopropylmalate dehydrogenase of a thermoacidophilic archaeon, Sulfolobus sp. strain 7.
abstract: The archaeal leuB gene encoding isopropylmalate dehydrogenase of Sulfolobus sp. strain 7 was cloned, sequenced, and expressed in Escherichia coli. The recombinant Sulfolobus sp. enzyme was extremely stable to heat. The substrate and coenzyme specificities of the archaeal enzyme resembled those of the bacterial counterparts. Sedimentation equilibrium analysis supported an earlier proposal that the archaeal enzyme is homotetrameric, although the corresponding enzymes studied so far have been reported to be dimeric. Phylogenetic analyses suggested that the archaeal enzyme is homologous to mitochondrial NAD-dependent isocitrate dehydrogenases (which are tetrameric or octameric) as well as to isopropylmalate dehydrogenases from other sources. These results suggested that the present enzyme is the most primitive among isopropylmalate dehydrogenases belonging in the decarboxylating dehydrogenase family.
authors.affiliation: Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: Y
authors.initials: Y
authors.lastname: Inoki
authors.forename: A
authors.initials: A
authors.lastname: Yamagishi
authors.forename: T
authors.initials: T
authors.lastname: Iwasaki
authors.forename: T
authors.initials: T
authors.lastname: Wakagi
authors.forename: T
authors.initials: T
authors.lastname: Oshima
mesh_terms: D050539:3-Isopropylmalate Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D001482:Base Composition; D001483:Base Sequence; D003001:Cloning, Molecular; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D013379:Substrate Specificity; D016944:Sulfolobus / Q000201:enzymology* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D000429:Alcohol Oxidoreductases; D050539:3-Isopropylmalate Dehydrogenase