Open AccessAutoxidation of Native Oxymyoglobin. Kinetic Analysis of the pH Profile
Author(s) -
SHIKAMA Keiji,
SUGAWARA Yoshiaki
Publication year - 1978
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1978.tb12693.x
Subject(s) - autoxidation , metmyoglobin , chemistry , myoglobin , reaction rate constant , dissociation (chemistry) , kinetics , catalysis , ion , dissociation constant , inorganic chemistry , photochemistry , organic chemistry , biochemistry , receptor , quantum mechanics , physics
The rate of autoxidation of native oxymyoglobin to metmyoglobin has been examined over the pH range of 4.8–12.6 in 0.1 M buffer at 25°C, and some 40 values of the observed first‐order rate constant, k obs are plotted against pH of the solution. In order to understand the k obs –pH profile thus obtained, some mechanistic models are proposed for the autoxidation reaction. The fitting of their rate equations as a function of pH has been examined to the experimental k obs –pH plot by a least‐squares method with the use of a digital computer. The complicated pH‐profile can be best explained by the ‘acid‐base catalyzed three states model’, which reveals not only the catalytic role of hydrogen ions and hydroxyl ions, but also the involvement of two dissociation groups of myoglobin molecule in the autoxidation reaction.