The heterogeneity of the protein content of liver and muscle glycogens

The portions of both liver and muscle glycogen that have a high protein content have been investigated. In liver the high molecular weight protions of glycogen may be rendered insoluble by treatment with trichloroacetic acid. This shows that reported desmo- (or insoluble) glycogen is an artefact of the extraction process and therefore of no physiological significance. In contrast, muscle glycogen isolubility is not associated with any specific molecular size range. Insolubility of muscle glycogen is shown to be related to partial degradation of the polysaccharide and to the high protein content remaining after the gentle extraction procedure. Since the molecular weight profile is unaltered by the removal of the insoluble glycogen it does not interfere with the interpretation of metabolic studies.