Carbohydrates in protein

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Abstract
The carbohydrate content of crystalline egg albumin becomes constant on re crystallization and the former can not be removed by denaturation or ultrafiltration. A method for the quantitative isolation of the carbohydrate group from egg albumin is described which is based on tryptic hydrolysis and involves no chemical treatment more drastic than acetylation and deacetylation under the mildest conditions. The poly-saccharide thus isolated is shown to have a mol. wt. of about 1200 and to be composed almost certainly of 4 molecules of mannose and two of glucosamine, together with an unidentified nitrogenous constituent. The complex is regarded as forming a single prosthetic group with one point of attachment to the molecule of natural egg albumin. The preparation and properties are described of 24-dihydroxy-benzylideneglucosamine, a compound useful for the isolation and characterization of glucosamine. The possible significance of the carbohydrate group in relation to the structure and immunological properties of egg albumin is briefly discussed.