Evidence for reaction at two binding sites in the oxidation of parsley plastocyanin by tris(1,10-phenanthroline)cobalt(III)

The effect of redox inactive complexes of charge 4+, 5+, 6+, and 7+ as competitive inhibitors for the [Co(phen)₃]³⁺ (phen = 1,10-phenanthroline) oxidation of parsley plastocyanin PCu(I) has been studied. The maximum effectiveness of the inhibitors is 53% (at pH 5.8) increasing to 61% (at pH 7.5). This is believed to represent the extent of reaction at the east face binding site close to Tyr 83. Some or all of the remaining reaction is at the His 87 north site.