Isolation of an acidic protein from the armadillo submandibular gland

An acidic protein fraction with an apparent molecular weight of 34 000 has been isolated from the Cetavlon-treated, mucin-free supernatant of the armadillo submandibular gland 0.01 M NaCl extract. This purified material, which was obtained in a yield of 0.45%/g wet gland, contains 24 mol % acidic amino acids and 4 mol % basic amino acids. Hexosamines, sialic acid, and neutral sugars represent 7% of the dry sample weight. In polyacrylamide gel and cellulose acetate electrophoresis, a single protein band was observed. The acidic protein fraction is highly reactive with the Lowry phenol reagent, giving a protein value 83% higher than that obtained by summation of its anhydrous amino acids, and is explained by the occurrence of peptide linkages peculiar to this material. The presence of other basophilic components besides mucus glycoproteins within the salivary gland of the armadillo may have physiological significance.