title: Two isocitrate dehydrogenases from a psychrophilic bacterium, Colwellia psychrerythraea.
abstract: Two structurally different monomeric and dimeric types of isocitrate dehydrogenase (IDH; EC 1.1.1.42) isozymes were confirmed to exist in a psychrophilic bacterium, Colwellia psychrerythraea, by Western blot analysis and the genes encoding them were cloned and sequenced. Open reading frames of the genes (icd-M and icd-D) encoding the monomeric and dimeric IDHs of this bacterium, IDH-M and IDH-D, were 2,232 and 1,251 bp in length and corresponded to polypeptides composed of 743 and 416 amino acids, respectively. The deduced amino acid sequences of the IDH-M and IDH-D showed high homology with those of monomeric and dimeric IDHs from other bacteria, respectively. Although the two genes were located in tandem, icd-M then icd-D, on the chromosomal DNA, a Northern blot analysis and primer extension experiment revealed that they are transcribed independent of each other. The expression of the monomeric and dimeric IDH isozyme genes in C. maris, a psychrophilic bacterium of the same genus as C. psychrerythraea, is known to be induced by low temperature and acetate, respectively, but no such induction in the expression of the C. psychrerythraea icd-M and icd-D genes was detected. IDH-M and IDH-D overexpressed in Escherichia coli were purified and characterized. In C. psychrerythraea, the IDH-M isozyme is cold-active whereas IDH-D is mesophilic, which is similar to C. maris that contains both cold-adapted and mesophilic isozymes of IDH. Experiments with chimeric enzymes between the cold-adapted monomeric IDHs of C. psychrerythraea and C. maris (IDH-M and ICD-II, respectively) suggested that the C-terminal region of the C. maris IDH-II is involved in its catalytic activity.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita 10-jo Nishi 8-chome, Sapporo 060-0810, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Maki
authors.forename: Mizuho
authors.initials: M
authors.lastname: Yoneta
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takada
mesh_terms: D034241:Alteromonadaceae / Q000201:enzymology* / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004795:Enzyme Stability; D016680:Genome, Bacterial / Q000235:genetics; D007521:Isocitrate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D007521:Isocitrate Dehydrogenase