Carp hemoglobin V. Effects of pH and P₆-inositol on autooxidation

Autooxidation of carp hemoglobin has been measured from 4-25°C with and without P₆-inositol. The rate was accelerated by the increase of proton concentration and/or the addition of P₆-inositol. As the rate increases the kinetics become more complex. In acidic media with P₆-inositol, the autooxidation is initially rapid which becomes slower subsequently but eventually proceeds very fast. The activation energy for autooxidation is about 19 kcal · mol^-1. The complicated kinetics are partly attributable to the fact that carp hemoglobin is incompletely oxygenated under these conditions and that various liganded molecules including partially oxidized species have different susceptibilities toward autooxidation.