title: Isolation of a multiheme protein with features of a hydrazine-oxidizing enzyme from an anaerobic ammonium-oxidizing enrichment culture.
abstract: 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 micromol/min.mg and 5.5 +/- 0.6 microM, respectively. Hydrazine (25 microM) induced an increase in the proportion of reduced form in the spectrum, whereas hydroxylamine (500 microM) 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.
authors.affiliation: Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Munetaka
authors.initials: M
authors.lastname: Shimamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishiyama
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shigetomo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Toyomoto
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kawahara
authors.forename: Kenji
authors.initials: K
authors.lastname: Furukawa
authors.forename: Takao
authors.initials: T
authors.lastname: Fujii
mesh_terms: D001421:Bacteria, Anaerobic / Q000201:enzymology* / Q000378:metabolism; D001426:Bacterial Proteins / Q000302:isolation & purification*; D003470:Culture Media; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000302:isolation & purification*; D006834:Hydrazines / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D006834:Hydrazines; C404449:heme protein, bacteria; C029424:hydrazine