Malonic Semialdehyde Reductase from the Archaeon Nitrosopumilus maritimus Is Involved in the Autotrophic 3-Hydroxypropionate/4-Hydroxybutyrate Cycle
Malonic Semialdehyde Reductase from the Archaeon Nitrosopumilus maritimus Is Involved in the Autotrophic 3-Hydroxypropionate/4-Hydroxybutyrate Cycle
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DOI：
10.1128/aem.03390-14
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发表时间：
2014-12
影响因子：
4.4
通讯作者：
J. Otte;Achim Mall;D. Schubert;M. Könneke;I. Berg
中科院分区：
文献类型：
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作者：
J. Otte;Achim Mall;D. Schubert;M. Könneke;I. Berg
摘要 最近描述的奇古菌门氨氧化古菌在海洋、地热和陆地环境中非常丰富。该门的所有特征代表都是需氧化能自养氨氧化剂，通过最近描述的 3-羟基丙酸/4-羟基丁酸循环的奇菌形式同化无机碳。尽管已在奇古菌基因组中鉴定出一些编码该循环酶的基因，但该循环的许多其他基因与其他物种的特征酶并不同源，因此无法通过生物信息学进行鉴定。在此，我们报告了养殖海洋 thaumarchaeon Nitrosopumilus maritimus 中丙二酸半醛还原酶 Nmar_1110 的鉴定和表征。该酶催化丙二酸半醛与 NAD(P)H 还原成 3-羟基丙酸，属于含铁醇脱氢酶家族，与来自橙色绿屈菌和景天金属球菌的丙二酸半醛还原酶不同源。它对丙二酸半醛具有高度特异性（Km，0.11 mM；V max，86.9 μmol min−1 mg−1 蛋白质），并且对琥珀酸半醛仅表现出较低的活性（Km，4.26 mM；V max，18.5 μmol min−1 mg−1 蛋白质）。 N. maritimus 丙二酸半醛还原酶的同源物可以在迄今为止测序的所有奇古菌基因组中找到，并在含铁醇脱氢酶的系统发育树中形成明确的簇。我们得出结论，丙二酸半醛还原酶可以被视为 3-羟基丙酸/4-羟基丁酸循环的奇菌版本的特征酶。
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; V max, 86.9 μmol min−1 mg−1 of protein) and exhibits only low activity with succinic semialdehyde (Km , 4.26 mM; V max, 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.