[Study of the carbohydrate component of cathepsin D]

A content of neutral sugars and N-acetyl-glucosamine in homogeneous cathepsin D preparations from a variety of vertebrate organs was determined. A more detailed study of the carbohydrate component was carried out with chicken liver cathepsin D preparation. It was shown that carbohydrates constitute 20% of the molecule of this cathepsin and contain glucosamine (11.6%) and mannose (10%). Removal of the major portion of the carbohydrates by treatment with mixture of glycosidases did not lead to any significant decrease of biological activity. This finding suggests that the carbohydrate component is not essential for the biological activity of the enzyme. Analysis of distribution of carbohydrates in the peptides of the trypsin hydrolyzate of cathepsin D allows conclusion that the enzyme molecule has several carbohydrate chains attached to different sites of the molecule.