Figure 4From: Purification and functional characterization of protoplasts and intact vacuoles from grape cellsProton pumping activity in intact vacuoles purified from grape protoplasts. The accumulation of protons was determined by measuring the fluorescence quenching of ACMA [14, 15] in 2 × 105 vacuoles. Typical fluorescence signals of the initial velocities of proton pumping by V-H+-PPase after addition of 0.1 to 150 μM PPi (A) and the corresponding Michaelis-Menten plot (B). Michaelis-Menten plot of the initial velocities of proton pumping by V-H+-ATPase as a function of ATP concentration (0.05 to 1.5 mM) (C). The results presented in B and C show the average values of two independent experiments.Back to article page