Glycogen synthesis by the direct or indirect pathways depends on glucose availability: in vivo studies in frog oocytes.
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.
Preller
Ana
A
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Region Metropolitana, Chile. apreller@uchile.cl
Kessi
Eduardo
E
Ureta
Tito
T
D000818:Animals; D001001:Anura / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D006003:Glycogen / Q000096:biosynthesis*; D007553:Isotope Labeling; D007700:Kinetics; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D014316:Tritium; D006003:Glycogen; D005947:Glucose