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J. Bacteriol., Feb 1997, 1174-1179, Vol 179, No. 4
T Suzuki, Y Inoki, A Yamagishi, T Iwasaki, T Wakagi and T Oshima
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.
Copyright © 1997, American Society for Microbiology
Molecular and phylogenetic characterization of isopropylmalate dehydrogenase of a thermoacidophilic archaeon, Sulfolobus sp. strain 7
Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan.
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