Intermolecular chemical heterogeneity of liver glycogen

Rabbit liver glycogen is shown to contain small amounts of covalently bound phosphate and glucosamine, and to display intermolecular heterogeneity with respect to the proportions of these two trace components. The difference in phosphate content over five fractions, separated on DEAE-cellulose, ranged from 2 to 155 molecular proportions relative to glycogen of Mr 10(7), while the glucosamine content varied from 0.6 to 2.3 molecular proportions. In parallel, the average molecular size and the turbidity of the glycogen fractions increased with increasing phosphate and glucosamine contents, the molecular weight profile taking the form of a change in the ratio of two glycogen components of distinctly different sizes. The varying presence of the phosphate and glucosamine, apart from their own significance, may help in gaining an insight into the overall properties of glycogen itself, such as the relative ages of individual molecules and the existence of different metabolic pools.