Chemical deglycosylation of carcinoembryonic antigen for amino acid sequence studies

Abstract

Two chemical methods are compared for the deglycosylation of the highly glycosylated glycoprotein, carcinoembryonic antigen (CEA). Solvolysis of CEA in anhydrous HF removed all of the carbohydrate except for N-glycosidically linked GlcNAc. CEA deglycosylated by HF solvolysis has a single polypeptide chain, which has been sequenced in high yield through the first 30 amino terminal residues. It retained 15% of its original antigenic activity in a radioimmunoassay and was able to inhibit up to 85% of the binding of intact CEA to anti-CEA. CEA deglycosylated by mild methanolysis had 3% carbohydrate remaining and was concomitantly split into at least 10 peptides, which appear to be amenable to further sequence studies.