Effect of PI(4,5)P2 on the activity of recombinant PTEN and variants K13E, R47K, and R47G in monomer and vesicle assay systems. The ratio of the specific activity with PI(4,5)P2 added to the activity in its absence is shown for WT and the three mutant proteins. In the monomer substrate mixture diC8PI(3,4)P2 is 0.1 mm with either 0.05 mm (■) or 0.1 mm (///) diC8PI(4,5)P2. Vesicles (▩) were composed of DOPI(3,4)P2/POPC (0.05 to 0.95 mm) with 0.05 mm DOPI(4,5)P2. The specific activities of wild type PTEN toward each substrate in the absence of PIP2 are 45 ± 4 nmol/mg min for diC8PI(3,4)P2 and 0.59 ± 0.02 nmol/mg min for DOPI(3,4)P2/POPC LUVs.