Partial structural analysis of concanavalin A binding glycopeptides of large size from human teratocarcinoma-derived cells: cleavage by hydrazinolysis and alkaline borohydride

Abstract

Pronase digests of cultured teratocarcinoma-derived cells (PA 1) of human origin have been previously shown to contain large-sized glycopeptides (relative mass (Mr) > 7400), of which 15–23% are retained by columns of concanavalin A (Con A) – Sepharose and can be eluted with 10 mM methyl α-D-mannopyranoside. The present data show that this fraction (A – Con A II) contains a family of glycopeptides that are degradable with anhydrous hydrazine as well as with 0.05 M NaOH – 1 M NaBH4. The cleavage products representing individual oligosaccharide chains, presumably as oligosaccharides and glycopeptides, consisted mostly of medium- (Mr 1400–6000) and small-sized (Mr < 1400) molecules. This implies that glycopeptides bearing several oligosaccharide chains were present in A – Con A II. Most of the individual oligosaccharide chains were not bound to Con A – Sepharose, but some were retained by the lectin column in the same way as the original glycopeptides. Some of the oligosaccharides were degraded partially with endo-β-galactosidase from Escherichia freundii suggesting the presence of GalβGlcNAcβ repeats. The present findings show that A – Con A II may be different from the "embryonic" glycopeptides of mouse teratocarcinoma cells that are reportedly not cleaved by mild alkaline borohydride treatment. Instead, A – Con A II is reminiscent of the T-1 glycopeptide of glycophorin.