Figure 1.

Surface pressure-PLC activity relationship for PIP₂-containing monolayers. A, Monolayers formed at an initial surface pressure of 20 mN/m and 20 μg of partially purified PLC from C. roseus transformed roots. Ca²⁺ (25 μm free Ca²⁺) was added to the subphase after 5 min. Results show a smooth trace, representative of five experiments performed at that pressure. B, PLC activity determined against monolayers formed at increasing initial surface pressures. Reaction time was 20 min after the addition of Ca²⁺ and data are expressed as percentage of lipid hydrolyzed per minute. Data are means of at least five experiments for each pressure and varied by less than 5%.