Ceruloplasmin substrate groups

This blue oxidase, present in the plasma of vertebrates, appears to be multifunctional.905,975 It accounts for some 95% of the circulating copper in a normal mammal, and its concentration fluctuates considerably in diseased states. It appears that ceruloplasmin has a major role in copper transport (as discussed in Section 62.1.11). In addition it has oxidase activity towards three groups of substrates, although its physiological role is not known with certainty. 

The enzyme catalyses the oxidation of L-ascorbic acid, 4, to dehydroascorbic, 5. The blue protein belongs to the group of blue oxidases together with laccase and ceruloplasmin. These are multicopper enzymes catalysing the electron reduction of molecular oxygen to water with concomitant one electron oxidation of the substrate. 

McDermott et al. (163) have proposed that there are two groups of substrates for ceruloplasmin those substances for which non-chelated Fe is not required and therefore which interact directly with the enzyme and those substrates which require the presence of non-chelated Fe to be catal3dically oxidized. Some substrates belonging to the former group are epinephrine, PPD, norepinephrine, dopamine, and serotonin. Those falling in the second class are ascorbate, hydro-quinone, ferrocyanide, L-DOPA, hydroxylamine, thioglycolic, acid and cysteine. 

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