title: Three inositol dehydrogenases involved in utilization and interconversion of inositol stereoisomers in a thermophile, Geobacillus kaustophilus HTA426.
abstract: Geobacillus kaustophilus HTA426, a thermophilic Bacillus-related species, utilizes some inositol stereoisomers, including myo-, d-chiro- and scyllo-inositols (MI, DCI and SI), as sole carbon sources. Within its genome are three paralogous genes that possibly encode inositol dehydrogenase. These genes are located in tandem within a large gene cluster containing an almost complete set of iol genes homologous to genes involved in inositol catabolism in Bacillus subtilis. Each of the three plausible inositol dehydrogenases was purified as a His(6)-tag fusion. The enzymes exhibited thermophilic activity, each with its own characteristic specificity for the inositol stereoisomers and cofactors. Northern blot and primer extension analyses revealed that the three enzymes were encoded by the same 5 kb polycistronic transcript and were induced simultaneously in the presence of MI. HTA426 was subjected to ethyl methanesulfonate (EMS) mutagenesis to isolate a mutant strain, PS8, which was not able to utilize MI. In PS8, inositol dehydrogenase activity was abolished along with the 5 kb transcript, suggesting that any of the three enzymes supports MI-dependent growth. Analysis of metabolites in HTA426 cells grown in the presence of MI revealed that substantial amounts of DCI and SI appeared intracellularly during the stationary phase, while only MI was present in PS8 cells, suggesting that interconversion of inositol stereoisomers may involve these three enzymes.
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Ken-Ichi
authors.initials: KI
authors.lastname: Yoshida
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Sanbongi
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Ayano
authors.initials: A
authors.lastname: Murakami
authors.affiliation: Organization of Advanced Science and Technology, Kobe University, Kobe 657-8501, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Takenaka
authors.affiliation: Microbial Genome Research Group, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Takami
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D056506:Geobacillus / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D006358:Hot Temperature; D007294:Inositol / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D013237:Stereoisomerism
chemical_list: D001426:Bacterial Proteins; D007294:Inositol; D010088:Oxidoreductases