The structure of placental glycogen

Glycogen was purified from human term placenta and its structural features investigated. The beta-amylolysis limit and average chain lengths indicated that some degradation of the glycogen had occurred prior to its extraction. The sedimentation coefficient distribution of the purified glycogen showed that it contained a significant proportion of aggregated material. Diffusion coefficient measurements allowed calculation of the molecular weight distribution. The placental glycogen contained a significant proportion of high molecular weight material, although not as much as liver or skeletal muscle glycogens. Because the high molecular weight glycogen of liver and skeletal muscle is associated with the lysosome it is likely that this is also true of the large placental glycogen. Lysosomal glycogen is degraded hydrolytically to glucose and so placental glycogen may be involved in fetal glucose homeostasis.