The Mucoproteins of the Snails, Helix Aspersa and Helix Pomatia

The problem of the structure of complex proteins containing carbohydrates in their molecule is still a subject of discussion. The fundamental questions which have been debated during the last decades and which have been the subject of many controversies are concerned with the nature of the carbohydrate group present in the molecule of these substances. Since the discovery of mucoproteins or mucins, as all of them were termed originally, three mutually antagonistic views were advanced. Chronologically, they were the following: All mucoproteins are physical mixtures of a polysaccharide, resembling dextrin, and proteins. The polysaccharide was termed “animal gum” (Landwehr’). Through the experimental criticism of Hammarsten,” this view was modified by its author and in its final form it assumed a chemical union between the animal gum and the protein. The second view, of more recent date, was that the carbohydrate complexes of all mucoproteins were conjugated sulfuric acids of the type of mucoitin sulfuric acid. The third theory presented the structure of this group of substances in the form of a peptide or glucosidic linking between simple sugars (amino sugars) and proteins. There were authorities who believed in the existence of representatives of each one of the three types of substances. Theoretically, every one of the three theories is possible and, therefore, the final decision will depend only on facts. However, the number of complex proteins containing carbohydrates in their molecules is very great and it will require much time and labor to analyze all of them.