Oncoprecipitins from marine invertebrates are glycoproteins with a higher specificity to carcinoembryonic antigen

Oncoprecipitins isolated from a number of marine invertebrates have been shown to be glycoproteins possessing a higher specificity to carcinoembryonic antigen (CEA)--similar to the interaction of antigen-antibody. The oncoprecipitin-CEA interaction was found to be substantially more specific than that of carbohydrate-containing polymers with lectins. Two oncoprecipitins, crustacin and cyprein, isolated from Pagurus prideauxii and Cyprea caputserpentis, respectively, have been characterized. The binding reaction of CEA with crustacin and cyprein failed to be inhibited with glycoproteins having sugar chain patterns closely related to those of CEA. Inhibition of the oncoprecipitin-CEA interaction with sugars was shown to be nonspecific and was observed only at sufficiently high concentrations of sugars used as inhibitors. Immunoenzymic assay of CEA content in normal and tumor tissues using CEA crustacin and CEA antiserum against CEA test systems revealed highly consistent results for both systems.