Figure 6. AthPEPCK1 activity is inhibited by dipeptides.

• A, B
  Recombinant AthPEPCK1 activity was measured at increasing concentrations of six different H–P dipeptides (A) or Tyr‐Asp (B). I _0.5 values are indicated on each graph. Measurements were performed in the decarboxylation direction, as described in the Methods section. Data were adjusted to a modified Hill equation. The value of 1 corresponds to the activity of 4.3 ± 0.2 U mg⁻¹. Data are mean ± SEM of 4 independent measurements.
• C
  PEPCK activity was measured in a protein lysate prepared from 3‐week‐old Arabidopsis leaves in the absence (control, C) or presence of 500 µM of the different dipeptides. Measurements were performed in the carboxylation direction, as described in the Methods section. Data are mean ± SE of 4 independent lysate preparations. Unpaired two‐tailed Student’s t‐tests were performed to compare dipeptide treatments with the control.