Isolation and characterization of a pulmonary glycoprotein from human amniotic fluid.

A glycoprotein of the molecular weight of 36 000 has been isolated from human amniotic fluid. The glycoprotein was found to contain sialic acid, galactose, mannose, fucose, glucosamine, hydroxyproline and relatively high amounts of glycine. End-group analyses resulted in a single NH2-terminal residue indicating that the glycoprotein was homogeneous. The data indicate that this unique collagen-like glycoprotein, which is immunologically identical to a major alveolar glycoprotein found in alveoli of patients with alveolar proteinosis, is also a major protein in the human amniotic fluid. The idea that the pulmonary constituents enter the amniotic fluid cavity during fetal lung development is also confirmed by this report.