Mechanism of the oxidation reaction of deoxyhemoglobin as studied by isolation of the intermediates suggests tertiary structure dependent cooperativity

The intermediates in the oxidation of deoxyhemoglobin by ferricyanide in 0.1 M KCl, at 20 o C and three pH values, were studied by cryogenic techniques. Data analysis was carried out according to a simple four rate constant model, ignoring the functional heterogeneity of the subunits, to simulate the time courses of the oxidation reaction, as studied by the stopped-flow technique [Antonini et al., (1965) Biochemistry 4, 345], which show anticooperativity at neutral pH and cooperativity at alkaline pH. Data analysis according to a 12 rate constant model indicated that the rate of oxidation of the β subunit in the first oxidation reaction was 4 times faster than the rate of oxidation of the β subunit at pH 6.2 and 12 times faster at pH 8.5