Some properties of coupled iron–caeruloplasmin oxidation systems

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Abstract
Some properties of coupled iron-caeruloplasmin oxidation systems have been investigated. Ferrous iron enhances the activity of caeruloplasmin against NN-dimethyl-p-phenyl-enediamine, the effect decreasing with increasing NN-dimethyl-p-phenylenediamine concentration and upon preincubation of iron with caeruloplasmin. Enhancement is prevented by ethylenediaminetetra-acetic acid or excess of protein. 5-Hydroxytryptamine and 5-hydroxy-indolyl -acetic acid are oxidized to indolic products by caeruloplasmin, the optima being about pH 5.5 and 4.5 respectively. Oxidation of 5-hydroxytryptamine by caeruloplasmin is neither inhibited by ethyl-enediamine tetraacetic acid nor enhanced by iron under the conditions used. Oxidation of 5-hydroxyindolylacetic acid is partly inhibited by ethylenediaminetetraacetic acid and greatly enhanced by iron. Oxidation of adrenaline to adrenochrome by caeruloplasmin is partly inhibited by ethylenediaminetetracetic acid and is enhanced by iron. The inhibition of caeruloplasmin by ethylendiaminetetracetic acid is discussed in the light of these and of earlier findings.