Protein phosphatase that specifically mediates dephosphorylation of 'Ser-586' of Akt1, a protein that regulates the balance between cell survival and apoptosis through a cascade that primarily alters the function of transcription factors that regulate pro- and antiapoptotic genes. Dephosphorylation of 'Ser-586' of Akt1 triggers apoptosis and suppression of tumor growth. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate