Suzuki T, Inoki Y, Yamagishi A, Iwasaki T, Wakagi T, Oshima T
Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan.
J Bacteriol. 1997 Feb;179(4):1174-9. doi: 10.1128/jb.179.4.1174-1179.1997.
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.
编码硫化叶菌属菌株7异戊二烯苹果酸脱氢酶的古菌leuB基因被克隆、测序，并在大肠杆菌中表达。重组硫化叶菌属酶对热极其稳定。该古菌酶的底物和辅酶特异性与细菌对应物相似。沉降平衡分析支持了早期的一项提议，即该古菌酶是同四聚体，尽管迄今为止所研究的相应酶据报道是二聚体。系统发育分析表明，该古菌酶与线粒体NAD依赖性异柠檬酸脱氢酶（为四聚体或八聚体）以及其他来源的异戊二烯苹果酸脱氢酶同源。这些结果表明，本酶是脱羧脱氢酶家族中异戊二烯苹果酸脱氢酶中最原始的。
