Association of enzymes with rat liver glycogen isolated by rate-zonal centrifugation.

1. Rat liver glycogen was separated into fractions of relatively uniform particle sizes by large volume rate-zonal centrifugation of tissue homogenates with the use of sucrose density gradients. 2. After centrifugation, the distribution curve obtained by plotting the glycogen content of all collected fractions exhibited its maximum a short centrifugal distance from the zone which contained the starting sample. The curve then decreased progressively until an abrupt increase was noted in the zone containing the isopycnically banded membranes. 3. The distribution curves for the cy-glucan phosphorylase and of UDP-glucose-glycogen transferase activities were similar to those for glycogen. 4. The phosphorylase-to-glycogen ratios decreased as the molecular weight of the glycogen particles increased, while the opposite was observed with the transferase-to-glycogen ratios. 5. The possible relationship between patterns of preferential binding of enzymes and the molecular weight spectra of glycogen characteristic of their origin are discussed.