Catalytic generation of N2O3 by the concerted nitrite reductase and anhydrase activity of hemoglobin.
Nitrite reacts with deoxyhemoglobin to form nitric oxide (NO) and methemoglobin. Though this reaction is experimentally associated with NO generation and vasodilation, kinetic analysis suggests that NO should not be able to escape inactivation in the erythrocyte. We have discovered that products of the nitrite-hemoglobin reaction generate dinitrogen trioxide (N2O3) via a novel reaction of NO and nitrite-bound methemoglobin. The oxygen-bound form of nitrite-methemoglobin shows a degree of ferrous nitrogen dioxide (Fe(II)-NO2*) character, so it may rapidly react with NO to form N2O3. N2O3 partitions in lipid, homolyzes to NO and readily nitrosates thiols, all of which are common pathways for NO escape from the erythrocyte. These results reveal a fundamental heme globin- and nitrite-catalyzed chemical reaction pathway to N2O3, NO and S-nitrosothiol that could form the basis of in vivo nitrite-dependent signaling. Because the reaction redox-cycles (that is, regenerates ferrous heme) and the nitrite-methemoglobin intermediate is not observable by electron paramagnetic resonance spectroscopy, this reaction has been 'invisible' to experimentalists over the last 100 years.
Basu
Swati
S
Department of Physics, Wake Forest University, 1834 Wake Forest Road, Winston-Salem, North Carolina 27109, USA.
Grubina
Rozalina
R
Huang
Jinming
J
Conradie
Jeanet
J
Huang
Zhi
Z
Jeffers
Anne
A
Jiang
Alice
A
He
Xiaojun
X
Azarov
Ivan
I
Seibert
Ryan
R
Mehta
Atul
A
Patel
Rakesh
R
King
Stephen Bruce
SB
Hogg
Neil
N
Ghosh
Abhik
A
Gladwin
Mark T
MT
Kim-Shapiro
Daniel B
DB
D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D009572:Nitrite Reductases / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009589:Nitrogen Oxides / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism
D006454:Hemoglobins; D009573:Nitrites; D009589:Nitrogen Oxides; C031701:nitrogen trioxide; D007501:Iron; D009572:Nitrite Reductases; D010100:Oxygen