A hepatic receptor of avian origin capable of binding specifically modified glycoproteins.

Evidence is reported to support the following conclusions: (i) The presence of a specific hepatic receptor capable of recognizing and binding galactose-terminated glycoproteins is responsible for maintaining near zero levels of circulating asialoglycoproteins in mammalian serum. (ii) The absence of this galactose-specific binding protein in avian, and presumably reptilian, liver is correlated with high levels of circulating asialoglycoproteins in the serum of these species. (iii) The evolutionary significance of these observations is reinforced by the recognition of an avian hepatic binding protein specific for terminal, N-acetyl-glucosamine residues on glycoproteins.