sentence: The B ′ subunits make extensive contacts to both , the scaffold and the catalytic subunits A and C of PP2A , and their acidic surface faces the active site of PP2A-C , allowing for substrate recognition.33 Based on the structure of the PP2A holoenzyme , the major role of the regulatory B-type subunits is to target substrate proteins to the phosphatase.33We have shown that CycG is an important regulator of growth and lipid metabolism in Drosophila , acting as a positive modulator of InR / TOR signaling activity at the PP2A / Akt1 nexus .