The enzymatic cleavage of rhodopsin by the retinal pigment epithelium. II. The carbohydrate composition of the glycopeptide cleavage product.

The carbohydrate groups present in the glycopeptide cleaved from purified [3H]-GlcNAc-rhodopsin by an enzyme from the retinal pigment epithelium were analyzed in terms of the size of the oligosaccharide chains, the sequence of the sugars and their anomeric linkages. These analyses were performed also on intact rhodopsin and an enzyme control. The oligosaccharides were cleaved from the peptide by means of hydrazinolysis. After reduction with NaB3H4, the oligosaccharides, purified by paper electrophoretic and paper chromatographic means, were digested sequentially with exoglycosidases, and the resultant digestion products examined by high-resolution gel filtration on Bio-Gel P-4 (-400). The size, sequence and anomeric configuration of the constituents of the oligosaccharides present in the glycopeptide were essentially identical to those present in intact purified rhodopsin, indicating the retention by the glycopeptide of the sugar chains of the intact molecule.