The Carbohydrate Moiety of Bovine Pancreatic Deoxyribonuclease

Abstract

Abstract Preceding experiments by Price and his associates establish that bovine pancreatic deoxyribonuclease is a glycoprotein which contains glucosamine and mannose. In order to determine the mode of attachment of the carbohydrate to the enzyme molecule, chromatographically purified deoxyribonuclease has been digested with Pronase. Gel filtration of the digest yielded a fraction containing all of the carbohydrate in association with a mixture of the dipeptide and tetrapeptide sequences Ser-Asp and Ser-Asp-Ala-Thr. Removal of serine by the Edman degradation demonstrated that all of the carbohydrate is in association with aspartic acid. Analyses of the glycopeptides showed 1 residue of ammonia, 2 residues of glucosamine, and 5 of mannose to be present per residue of aspartic acid. Since only 2 residues of glucosamine (assumed to occur as the N-acetyl derivative) are present in the parent molecule, it is concluded that the saccharide moiety is attached at a single position on the enzyme and through an aspartamido-hexose linkage.