11.2.3.1.2 Conalbumin (Ovotransferrin)
Conalbumin and serum transferring are identical in the chicken. This protein, unlike ovalbumin, is not denatured at the interphase but coagulates at lower temperatures. Conalbumin consists of one peptide chain and contains one oligosaccharide unit made of four mannose and eight N-acetylglucosamine residues.
Binding of metal ions (2 moles Mn3+ , Fe3+ , Cu2+ or Zn2+ per mole of protein) at pH 6 or above is a characteristic property of conalbumin. Table 11.6 lists the absorption maxima of several complexes. The occasional red discoloration of egg products during processing originates from a conalbumin-iron complex. The complex is fully dissociated at a pH less than 4. Tryosine and histidine residues are involved in metal binding. Alkylation of 10 to 14 histidine residues with bromoacetate or nitration of residues with tetranitromethane removes its iron-binding ability. Conalbumin has the ability to retard growth of microorganisms.