Isolation of gastroferrin from human gastric juice

A method is reported for the isolation of gastroferrin - the high molecular weight iron-binding fraction of human gastric juice. This method is based on the ability of the iron-gastroferrin complex to be removed from solution by coprecipitation with ferric hydroxide. When iron is removed from the iron-gastroferrin complex, the gastroferrin is shown to regain its iron chelating ability. Preliminary examination of the product so obtained showed it to be a glycoprotein of molecular weight 260,000. It consists of approximately 85% carbohydrate and 15% protein. Glucosamine, galactosamine, galactose, fucose, and sialic acid were the only carbohydrate residues detected. Serine, threonine, and proline predominated among the 17 amino acids observed; aromatic and sulfur containing amino acids were present in only small amounts.