Figure 7. Enzymatic activity of Lactococcus lactis PYK at various concentrations of Pi and FBP.

Panel A shows experimental measurements of the PYK activity at an increasing Pi concentration with 0 mM, 2 mM, 10 mM and 30 mM FBP present as reported by Mason et al. [12]. Panel B shows the simulation results of the PYK kinetic model. The kinetic model is able to predict the PYK activity for 0 mM, 2 mM and 10 mM FBP, but somewhat underestimates the activity for 30 mM FBP. According to this model, about 14 mM FBP is required to achieve the half maximum PYK activity (0.2) at a physiological Pi concentration of 4 mM (see text for details).