Protein phosphatase that inactivates multifunctional CaM kinases such as CAMK4 and CAMK2. Dephosphorylates and inactivates PAK. May play a role in the inhibition of actin fiber stress breakdown and in morphological changes driven by TNK2/CDC42. Inactivates multifunctional CaM kinases. Dephosphorylates PRKAA2 (By similarity). H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. Heterotrimer. Interacts with PAX1 and ARHGEF6 (or ARHGEF7) (By similarity). A truncated form, major form, with the C-terminal part missing, is mostly found in the cytoplasm and a little in the nucleus throughout the central nervous system. Although in some large neurons, the full-length, minor form, is found in the nucleus. Highly expressed in brain especially in hippocampus, thalamus and midbrain and to a lower extent in heart and spinal cord. Weakly expressed in testis. A very slow signal is also observed in heart, kidney and liver. Belongs to the PP2C family.