The presence in the retina of the pathway of glycoprotein biosynthesis involving the lipid-activation of carbohydrates as their dolichol-phosphate derivatives has been demonstrated by our previous studies. We are examining the role of this pathway in the biosynthesis of the specific glycoprotein, rhodopsin. Our studies are now concerned with the assembly of the N-acetyl-glucosaminyl linkage region and the regulation by the retina of the synthesis of the core-region oligosaccharide lipid. While the biosynthesis of rhodopsin occurs in the retina, its degradation and turnover involves the cells of the pigment epithelium. We are examining the properties of exo and endoglycosidases of the pigment epithelium and their action on the carbohydrate groups of rhodopsin.