Structural studies on carcinoembryonic antigen. Periodate oxidation.

Periodate oxidation has been applied to examine the carbohydrate structure of carcinoembryonic antigen (CEA) and the possible role of the carbohydrate residues in its antigenic activity. Sialic acid (N-acetylneuraminic acid) and fucose were completely destroyed, and galactose and mannose were partially destroyed by a single periodate treatment. Serial periodate treatment (Smith degradation) destroyed additional amounts of galactose and mannose as well as significant amounts of N-acetylglucosamine. Prior removal of sialic acid by neuraminidase treatment led to increased destruction of galactose by periodate. Antigenic activity persisted indicating that the residues destroyed played little, if any, part in the antigenicity of CEA. These results yield an initial view of the structural arrangement of the carbohydrate residues in the CEA molecule.