Acts as a lipid phosphatase, removing the phosphate in the D3 position of the inositol ring from phosphatidylinositol 3,4,5-trisphosphate. Shows no phosphoinositide phosphatase activity. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3,4,5-trisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + phosphate Isoform 3 is expressed in testis, brain and stomach while isoform 4 seems to be testis-specific. Expressed in testis, strongly inhibits cell growth in HeLa cells.