Interaction of ceruloplasmin, lactoferrin, and myeloperoxidase

Abstract

When lactoferrin (LF) and myeloperoxidase (MPO) are added to ceruloplasmin (CP), a CP-LF-MPO triple complex forms. The complex is formed under physiological conditions, but also in the course of SDS-free PAGE. Polyclonal antibodies to both LF and MPO displace the respective proteins from the CP-LF-MPO complex. Similar replacement is performed by a PACAP38 fragment (amino acids 29-38) and protamine that bind to CP. Interaction of LF and MPO with CP-Sepharose is blocked at ionic strength above 0.3 M NaCl and at pH below 4.1 (LF) and 3.9 (MPO). Two peptides (amino acids 50-109 and 929-1012) were isolated by affinity chromatography from a preparation of CP after its spontaneous proteolytic cleavage. These peptides are able to displace CP from its complexes with LF and MPO. Both human and canine MPO could form a complex when mixed with CP from seven mammalian species. Upon intravenous injection of human MPO into rats, the rat CP-human MPO complex could be detected in plasma. Patients with inflammation were examined and CP-LF, CP-MPO, and CP-LF-MPO complexes were revealed in 80 samples of blood serum and in nine exudates from purulent foci. These complexes were also found in 45 samples of serum and pleural fluid obtained from patients with pleurisies of various etiology.

Effect of lactoferrin on oxidative features of ceruloplasmin

“…Indeed, Lf is released from neutrophilic leukocytes and, according to our data, its whole bulk binds to Cp of plasma in molar ratio 1:1 (Sokolov et al 2007). The progress of inflammation is accompanied by tissue necrosis causing an increment to ferrous iron pool.…”

“…-binding site located nearby can get altered so that the affinity towards the substrate increases. Perhaps the high-affinity site is partly composed of the amino acid stretches 50-109 and 929-1,012 that were spotted previously as Lf-binding sequences in Cp (Sokolov et al 2007). These stretches provide ligands for type I Cu 2?…”

“…Then resin was precipitated by centrifugation (100g, 5 min) and Lf concentrations in supernatant portions from both test-tubes were assessed by rocket immunoelectrophoresis with polyclonal antibodies (Laurell 1967). Antibodies had been obtained by immunizing rabbits with Lf (Sokolov et al 2007). Concentration of Lf not bound to Cp-Sepharose was denoted as [F].…”

“…To our knowledge Lf is the only protein among transferrins that is able to stimulate Cp as ferroxidase. Selective interaction between Cp and Lf is evidenced by formation of their complex revealed in the blood plasma of patients with various pathologies (Sokolov et al 2007) and in colostrum of healthy women (Sokolov et al 2006). The complex is the only breast milk component with ferroxidase activity, i.e., the whole bulk of Cp in milk interacts with Lf.…”

Ceruloplasmin Is an Endogenous Inhibitor of Myeloperoxidase

“…It is an abundant acute phase protein that has been demonstrated to interact with myeloperoxidase in plasma (20,21). Ceruloplasmin binds to myeloperoxidase with a binding constant of 7.5 ϫ 10 6 M Ϫ1 (22).…”