Specific oxidase activity of cord serum ceruloplasmin in the newborn

In a study of 50 full-term newborns, we found serum levels of ceruloplasmin , its oxidase activity and specific oxidase activity (activity per unit mas s of enzyme protein) which were significantly lower than in adult subjects (p<0.001). A significant correlation was obtained between the specific oxid ase activity of the neonatal ceruloplasmin and the transferrin/<alpha>-feto protein ratio (p<0.01), which reflects the maturity of the fetal hepatocyte through its ability to synthesise fetal and non-fetal-associated proteins. The lower specific oxidase activity of the ceruloplasmin in newborns would be due to a higher relative proportion of apoprotein, and/or other molecul ar forms with a poor copper content in the oxidase sites. This could be due to an inability to transfer copper into a common intracellular pool for ho loceruloplasmin synthesis and biliary copper excretion. A high interindivid ual variability was found for the specific oxidase activity of the neonatal ceruloplasmin, and in the newborns with higher levels of ceruloplasmin thi s, from a catalytic point of view, is more similar to the adult form.