title: Malonic semialdehyde reductase from the archaeon Nitrosopumilus maritimus is involved in the autotrophic 3-hydroxypropionate/4-hydroxybutyrate cycle.
abstract: The recently described ammonia-oxidizing archaea of the phylum Thaumarchaeota are highly abundant in marine, geothermal, and terrestrial environments. All characterized representatives of this phylum are aerobic chemolithoautotrophic ammonia oxidizers assimilating inorganic carbon via a recently described thaumarchaeal version of the 3-hydroxypropionate/4-hydroxybutyrate cycle. Although some genes coding for the enzymes of this cycle have been identified in the genomes of Thaumarchaeota, many other genes of the cycle are not homologous to the characterized enzymes from other species and can therefore not be identified bioinformatically. Here we report the identification and characterization of malonic semialdehyde reductase Nmar_1110 in the cultured marine thaumarchaeon Nitrosopumilus maritimus. This enzyme, which catalyzes the reduction of malonic semialdehyde with NAD(P)H to 3-hydroxypropionate, belongs to the family of iron-containing alcohol dehydrogenases and is not homologous to malonic semialdehyde reductases from Chloroflexus aurantiacus and Metallosphaera sedula. It is highly specific to malonic semialdehyde (Km, 0.11 mM; Vmax, 86.9 μmol min(-1) mg(-1) of protein) and exhibits only low activity with succinic semialdehyde (Km, 4.26 mM; Vmax, 18.5 μmol min(-1) mg(-1) of protein). Homologues of N. maritimus malonic semialdehyde reductase can be found in the genomes of all Thaumarchaeota sequenced so far and form a well-defined cluster in the phylogenetic tree of iron-containing alcohol dehydrogenases. We conclude that malonic semialdehyde reductase can be regarded as a characteristic enzyme for the thaumarchaeal version of the 3-hydroxypropionate/4-hydroxybutyrate cycle.
authors.affiliation: Mikrobiologie, Fakultät Biologie, Universität Freiburg, Freiburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Otte
authors.affiliation: Mikrobiologie, Fakultät Biologie, Universität Freiburg, Freiburg, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Mall
authors.affiliation: Mikrobiologie, Fakultät Biologie, Universität Freiburg, Freiburg, Germany.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Schubert
authors.affiliation: Organic Geochemistry Group, MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Könneke
authors.affiliation: Mikrobiologie, Fakultät Biologie, Universität Freiburg, Freiburg, Germany M. V. Lomonosov Moscow State University, Moscow, Russia ivan.berg@biologie.uni-freiburg.de.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Berg
mesh_terms: D001105:Archaea / Q000201:enzymology* / Q000235:genetics; D016000:Cluster Analysis; D006885:Hydroxybutyrates / Q000378:metabolism*; D007700:Kinetics; D019344:Lactic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D008315:Malondialdehyde / Q000031:analogs & derivatives* / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D006885:Hydroxybutyrates; C111420:4-hydroxybutyric acid; D019344:Lactic Acid; D008315:Malondialdehyde; D009249:NADP; C039786:malonic semialdehyde; C031601:hydracrylic acid; D010088:Oxidoreductases