Fig. 8: XPK serves as a CBB cycle brake under low ATP conditions.
From: An ATP-sensitive phosphoketolase regulates carbon fixation in cyanobacteria
Under normal ATP conditions (>1 mM), which occur at sufficient light or during dark periods when respiration is fully functional and CBB stops due to the lack of reducing power, XPK is inhibited and serves no function; however, during sudden environmental changes (for example self-shading and high-frequency light fluctuation), the ATP level drops and XPK is relieved from inhibition. XPK then diverts the CBB intermediate to stop CO2 fixation and produces AcP, which is then converted to acetate and ATP.
