期刊
JOURNAL OF INORGANIC BIOCHEMISTRY
卷 100, 期 4, 页码 542-550出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.jinorgbio.2005.12.012
关键词
hemoglobin; myoglobin; flavohemoglobin; nitric oxide; dioxygenase
资金
- NHLBI NIH HHS [HL 47020] Funding Source: Medline
- NIGMS NIH HHS [T32 GM008280, T32 GM 008280, GM 35649, GM 65090] Funding Source: Medline
Distantly related members of the hemoglobin (Hb) superfamily including red blood cell Hb, muscle myoglobin (Mb) and the microbial flavohemoglobin (flavoHb) dioxygenate nitric oxide ((NO)-N-.). The reaction serves important roles in (NO)-N-. metabolism and detoxification throughout the aerobic biosphere. Analysis of the stoichiometric product nitrate shows greater than 99% double O-atom incorporation from Hb 18O(2) Mb O-18(2) and flavoHb O-18(2) demonstrating a conserved high fidelity (NO)-N-. dioxygenation mechanism. Whereas, reactions of NO with the structurally unrelated Turbo cornutus MbO(2) or free superoxide radical (O--(2).) yield sub-stoichiometric nitrate showing low fidelity O-atom incorporation. These and other results support a (NO)-N-. dioxygenation mechanism involving (1) rapid reaction of (NO)-N-. with a FeIII-O-2(.) intermediate to form Fe-III-OONO and (2) rapid isomerization of the Fe-III-OONO intermediate to form nitrate. A sub-microsecond isomerization event is hypothesized in which the O-O bond homolyzes to form a protein caged [Fe-IV= (ONO2)-N-.] intermediate and ferryl oxygen attacks (NO2)-N-. to form nitrate. Hb functions as a (NO)-N-. dioxygenase by controlling O-2 binding and electrochemistry, guiding (NO)-N-. diffusion and reaction, and shielding highly reactive intermediates from solvent water and biomolecules. (c) 2005 Elsevier Inc. All rights reserved.
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