Oxidation of (horse) hemoglobin by copper: an intermediate detected by electron spin resonance

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Abstract
The oxidation of horse Hb by Cu(II) was followed by the changes in ESR spectra of copper. Stopped-flow and freeze-quenching techniques show that the 2nd-order rate constant for the binding of Cu(II) to Hb is > 5 .times. 105 mol-1 s-1 and the apparent 1st-order rate for the reduction of Cu(II) to Cu(I) is 0.051 s-1. The binding of Cu(II) to Hb is followed by an alteration of the Cu(II) spectrum, decreasing the g values. This process has an apparent rate constant of 17 s-1 and presumably involves a conformational change in the region of the Cu binding site. This conformational change is apparently necessary for Cu(II) to oxidize Hb.