Changes in Nitric Oxide Generated by the Oxidation of Oxymyoglobin by Nitrite

Abstract

We found that nitric oxide (NO) was produced during the oxidation of oxymyoglobin by nitrite, by using a NO-selective electrode system, which enabled us to measure NO in phosphate solution, continuously and quantitatively. When 500 μM nitrite was added in the solution of oxymyoglobin (65 μM in heme), oxymyoglobin was oxidized to metmyoglobin in a sigmoidal manner. During the reaction, NO was generated quickly at the initial lag phase, and reached its peak (NO approximated to 30 μM), before the burst oxidation of oxymyoglobin occurred. Then, NO content was gradually decreased. By the addition of the increased concentration of nitrite (1 mM or 2 mM) to oxymyoglobin solution (65 μM in heme), the production rate of NO was much accelerated and the amounts of NO were increased, in good accordance with the accelerated oxidation of oxymyoglobin by nitrite. These results suggest that NO is involved in the oxidation of oxymyoglobin by nitrite.