Isolation of a multiheme protein with features of a hydrazine-oxidizing enzyme from an anaerobic ammonium-oxidizing enrichment culture.
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.
Shimamura
Munetaka
M
Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
Nishiyama
Takashi
T
Shigetomo
Hiroyuki
H
Toyomoto
Takeshi
T
Kawahara
Yuka
Y
Furukawa
Kenji
K
Fujii
Takao
T
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
D001426:Bacterial Proteins; D003470:Culture Media; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D006834:Hydrazines; C404449:heme protein, bacteria; C029424:hydrazine