Ammonia-oxidizing bacteria (AOB) convert ammonia (NH₃) to nitrite (NO₂^–) as their primary metabolism and thus provide a blueprint for the use of NH₃ as a chemical fuel. The first energy-producing step involves the homotrimeric enzyme hydroxylamine oxidoreductase (HAO), which was originally reported to oxidize hydroxylamine (NH₂OH) to NO₂^–. HAO uses the heme P460 cofactor as the site of catalysis. This heme is supported by seven other c hemes in each monomer that mediate electron transfer. Heme P460 cofactors are c-heme-based cofactors that have atypical protein cross-links between the peptide backbone and the porphyrin macrocycle. This cofactor has been observed in both the HAO and cytochrome (cyt) P460 protein families. However, there are differences; specifically, HAO uses a single tyrosine residue to form two covalent attachments to the macrocycle whereas cyt P460 uses a lysine residue to form one. In Nitrosomonas europaea, which expresses both HAO and cyt P460, these enzymes achieve the oxidation of NH₂OH and were both originally reported to produce NO₂^–. Each can inspire means to effect controlled release of chemical energy.

中文翻译：

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血红素P460：与一氧化氮的交叉连接

氨氧化细菌（AOB）转换氨（NH ₃）亚硝酸盐（NO ₂ ^- ）作为主要的代谢，并因此提供了使用NH的蓝图₃作为化学燃料。所述第一能量产生步骤涉及同源三聚体酶羟胺氧化还原酶（HA0），其最初被报告给氧化羟胺（NH ₂ OH），以NO ₂ ^- 。HAO使用血红素P460辅助因子作为催化位点。此血红素由其他七个支持Ç血红素在每个单体中，其介导的电子转移。血红素P460辅助因子是c肽主链和卟啉大环之间具有非典型蛋白质交联的基于血红素的辅酶。在HAO和细胞色素（cyt）P460蛋白家族中均已观察到该辅助因子。但是，存在差异。具体而言，HAO使用一个酪氨酸残基形成两个与大环的共价连接，而Cyt P460使用赖氨酸残基形成一个。在欧洲亚硝化，其表达都HAO和细胞色素P460，这些酶实现NH的氧化₂ OH和均被最初报告产生NO ₂ ^- 。每个人都可以激发实现化学能受控释放的手段。