We have previously shown that iron-containing human lactoferrin (LF) purified from breast milk is able to form both in vitro and in vivo a complex with ceruloplasmin (CP), the copper-containing protein of human plasma. Here we present evidence that the CP-LF complex is dissociated by high concentrations of NaCl, CaCl2, or EDTA, or by decreasing the pH to 4.7. In addition, DNA, bacterial lipopolysaccharide, and heparin can displace CP from its complex with LF. Antibodies to either of the two proteins also cause dissociation of the complex.
Pulina MO, Zakharova ET, Sokolov AV, Shavlovski MM, Bass MG, Solovyov KV, Kokryakov VN, Vasilyev VB. (2002) Studies of the ceruloplasmin-lactoferrin complex.// Bioch. Cell. Biol. V. 80. P. 35-39.

In our previous report we first described a complex between lactoferrin (Lf) and ceruloplasmin (Cp) with K (d) ~ 1.8 muM. The presence of this complex in colostrum that never contains more than 0.3 muM Cp questions the reliability of K (d) value. We carefully studied Lf binding to Cp and investigated the enzymatic activity of the latter in the presence of Lf, which allowed obtaining a new value for K (d) of Cp-Lf complex. Lf interacting with Cp changes its oxidizing activity with various substrates, such as Fe(2+), o-dianisidine (o-DA), p-phenylenediamine (p-PD) and dihydroxyphenylalanine (DOPA). The presence of at least two binding sites for Lf in Cp molecule is deduced from comparison of substrates' oxidation kinetics with and without Lf. When Lf binds to the first site affinity of Cp to Fe(2+) and to o-DA increases, but it decreases towards DOPA and remains unchanged towards p-PD. Oxidation rate of Fe(2+) grows, while that of o-DA, p-PD and DOPA goes down. Subsequent Lf binding to the second center has no effect on iron oxidation, hampers DOPA and o-DA oxidation, and reduces affinity towards p-PD. Scatchard plot for Lf sorbing to Cp-Sepharose allowed estimating K (d) for Lf binding to high-affinity (~13.4 nM) and low-affinity (~211 nM) sites. The observed effect of Lf on ferroxidase activity of Cp is likely to have physiological implications.
Sokolov AV, Ageeva KV, Pulina MO, Zakharova ET, Vasilyev VB. (2009) Effect of lactoferrin on oxidative features of ceruloplasmin.// Biometals, V. 22, P. 521-529.