Stoichiometry of the reaction of oxyhemoglobin with nitrite.
During the reaction of oxyhemoglobin (HbO2) with nitrite, the concentration of residual nitrite, nitrate, oxygen, and methemoglobin (Hb+) was determined successively. The results obtained at various pH values indicate the following stoichiometry for the overall reaction: 4HbO2 + 4NO2- 4H+ leads to 4Hb+ + 4NO3- + O2 + 2H2 O (Hb denotes hemoglobin monomer). NO2- binds with methemoglobin noncooperatively with a binding constant of 340 M-1 at pH 7.4 and 25 degrees C. Thus, the major part of Hb+ produced is aquomethemoglobin, not methemoglobin nitrite, when less than 2 equivalents of nitrite is used for the oxidation.
D006441:Hemoglobin A; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008706:Methemoglobin; D009573:Nitrites; D010108:Oxyhemoglobins
D009573:Nitrites; D010108:Oxyhemoglobins; D008706:Methemoglobin; D006441:Hemoglobin A