Figure 4. The central control glycogen circuitry (modified from Figure 3.1 in [43]).

Rectangles and circles enclose the names or abbreviations of enzymes and substrates accordingly. The reactions as a result of an increase in cAMP concentrations are shown with bold arrows. cAMP = cyclic adenosine monophosphate; R2C2 = cAMP dependent protein kinase; C = R2C2 catalytic subunit; PKb = inactive phosphorylase kinase; PKa = active phosphorylase kinase; GPb = inactive glycogen phosphorylase; GPa = active glycogen phosphorylase; GSb = inactive glycogen phosphorylase; GSb = inactive glycogen synthase; GSa = active glycogen synthase; P = phosphate; g-6-p = glucose-6-phosphate; PP1, protein phosphatase-1.