Heterogeneity of carcinoembryonic antigen. I. Concanavalin A-reactive and -nonreactive CEA

The use of Con A-Sepharose affinity chromatography for preparation of CEA from two metastatic liver tumors resulted in a separation of two species of CEA. One is concanavalin A-reactive CEA (CEA-M): the other is Con A-nonreactive CEA (CEA-P). Both CEA-M and CEA-P were glycoproteins and have identical antigenicity. However, 4 samples of CEA-M and CEA-P subfractions differed in their protein:carbohydrate ratios. The yield of CEA-M was greater than that of CEA-P. In electrophoresis, both CEA-M and CEA-P migrated at the region of beta-globulin of human blood serum. The isoelectric points of 4 samples of CEA-M and CEA-P subfractions from two different tumor sources differed from each other. In these preparations CEA-M usually showed a larger value of isoelectric point than CEA-P. Ultracentrifugal analysis of these four preparations revealed only a single peak, except CEA-P in case 1. Antigenic activity of CEA-M was almost completely destroyed by beta-N-acetylhexosaminidase treatment but only partly digestion with pronase. A possibility was suggested that N-acetylglucosamine at nonreducing terminal(s) is essential for the antigenic determinant groups of CEA molecule.