The nitrite reductase activity of ferrous human hemoglobin:haptoglobin 1-1 and 2-2 complexes

Haptoglobin binding to hemoglobin is crucial to prevent extra-erythrocytic hemoglobin-induced damage; in turn, haptoglobin:hemoglobin complexes display heme-based reactivity catalyzing the conversion of NO2− to NO, which is followed by heme-Fe(II) nitrosylation.154