Chemiluminescence of Pholasin caused by peroxynitrite

The kinetics of the oxidation of Pholasin by peroxynitrite, which leads to emission of light, were studied. The reaction shows a lag phase, which is smaller at higher peroxynitrite-to-Pholasin ratios. The total light emission approximately doubles from pH 5 to 9 and decreases precipitously to half the pH 5 value at pH 10. Dioxygen and carbon dioxide accelerate the reaction course, but they do not change significantly the reaction yield. Chemiluminescence of Pholasin is suppressed by antioxidants, but no significant shift is noticed in the time at which light emission is maximal. The chemiluminescence intensity is strongly dependent on the potassium concentration, although it is not significantly affected by lithium, cesium, or magnesium; potassium decreases luminescence. The mechanism of the peroxynitrite-induced oxidation of Pholasin may start with the reversible formation of a protein-peroxynitrite intermediate, or a first oxidation product, followed in subsequent steps by decomposition and light emission. However, many questions concerning the mechanism of the light emission remain to be elucidated.