Fig. 1.

Effects of pH and free Ca²⁺ concentration on hydrolysis of XY-69 by PLC-γ1 (D1165H). (a) pH effect. Lipid vesicles consisting of PE (192 μM), PIP₂ (48 μM), and XY-69 (0.5 μM) in assay buffers with varying pH were added to PLC-γ1 (D1165H) (1 nM) at 20 °C or 30 °C. The initial velocity of XY-69 hydrolysis was measured and plotted against pH. The free Ca²⁺ concentration was 390 nM. (b) Effect of free Ca²⁺ concentration. The initial velocity of XY-69 (0.5 μM) hydrolysis by PLC-γ1 (D1165H) (1 nM) was measured with varying concentrations of free Ca²⁺ in the assay buffer (pH 7.4) at 20 °C or 30 °C