Isolation of a multiheme protein with features of a hydrazine-oxidizing enzyme from an anaerobic ammonium-oxidizing enrichment culture
Isolation of a multiheme protein with features of a hydrazine-oxidizing enzyme from an anaerobic ammonium-oxidizing enrichment culture
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DOI：
10.1128/aem.01978-06
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发表时间：
2007-02-01
影响因子：
4.4
通讯作者：
Fujii, Takao
中科院分区：
文献类型：
--
作者：
Shimamura, Munetaka;Nishiyama, Takashi;Fujii, Takao
从来自厌氧氨氧化细菌菌株KSU-1占优势的反应器的富集培养物中纯化具有肼氧化活性的多血红素蛋白。该酶对肼有氧化活性，但对羟胺没有氧化活性，是一种130 kDa的同源二聚体，由一个62 kDa的多肽组成，含有8个血红素。因此，它被命名为肼氧化酶（HZO）。以细胞色素c作为电子受体，肼的Vmax和K-m分别为6.2 +/- 0.3 μ mol/min中心点mg和5.5 +/- 0.6 μ M。肼（25 μ M）诱导光谱中还原形式的比例增加，而羟胺（500 μ M）没有。在来自培养物的宏基因组DNA中鉴定了编码HZO的两个基因hzoA和hzoB。除了两个残基外，这些基因编码相同的氨基酸序列。从这些基因推导的序列显示低水平的同源性（< 30%），所有的羟胺氧化还原酶的报告，但高度同源的两个hao基因通过测序的“Kuenenia stuttgartiensis”的基因组（88%和89%的同源性）。因此，纯化的酶可能是一种新的肼氧化酶在厌氧氨氧化的关键作用。
A multiheme protein having hydrazine-oxidizing activity was purified from enriched culture from a reactor in which an anammox bacterium, strain KSU-1, was dominant. The enzyme has oxidizing activity toward hydrazine but not hydroxylamine and is a 130-kDa homodimer composed of a 62-kDa polypeptide containing eight hemes. It was therefore named hydrazine-oxidizing enzyme (HZO). With cytochrome c as an electron acceptor, the V-max and K-m for hydrazine are 6.2 +/- 0.3 mu mol/min center dot mg and 5.5 +/- 0.6 mu M, respectively. Hydrazine (25 mu M) induced an increase in the proportion of reduced form in the spectrum, whereas hydroxylamine (500 mu M) did not. Two genes coding for HZO, hzoA and hzoB, were identified within the metagenomic DNA from the culture. The genes encode the same amino acid sequence except for two residues. The sequences deduced from these genes showed low-level identities (< 30%) to those of all of the hydroxylamine oxidoreductases reported but are highly homologous to two hao genes found by sequencing the genome of "Candidatus Kuenenia stuttgartiensis" (88% and 89% identities). The purified enzyme might therefore be a novel hydrazine-oxidizing enzyme having a critical role in anaerobic ammonium oxidation.