Glycogen synthesis by the direct or indirect pathways depends on glucose availability: in vivo studies in frog...

Besides the classic direct route, frog oocytes incorporate glucosyl units into glycogen by the so-called indirect pathway. The operation of both pathways depends on glucose availability. Below 0.5 mM glucose (calculated intracellular concentration), the indirect route accounts for 90% of polysaccharide formation, while the direct pathway supports 70% of total glucose incorporation when administered glucose is above 1.5 mM. A sigmoidal curve was obtained for the direct pathway with n(H)=2.04, and half saturation was reached at 2.6 mM glucose. The curve for the indirect route presented an n(H) of 1.15 and an S(0.5) of 0.9 mM glucose.