The PI(3,5)P2 regulatory complex regulates both the synthesis and turnover of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2). In vitro, hydrolyzes all three D5-phosphorylated polyphosphoinositide substrates in the order PtdIns(4,5)P2 > PtdIns(3,5)P2 > PtdIns(3,4,5)P3. Plays a role in the biogenesis of endosome carrier vesicles (ECV) / multivesicular bodies (MVB) transport intermediates from early endosomes. Dual specificity phosphatase component of the PI(3,5)P2 regulatory complex which regulates both the synthesis and turnover of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2). Catalyzes the dephosphorylation of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) to form phosphatidylinositol 3-phosphate. Has serine-protein phosphatase activity acting on PIKfyve to stimulate its lipid kinase activity, its catalytically activity being required for maximal PI(3,5)P2 production. In vitro, hydrolyzes all three D5-phosphorylated polyphosphoinositide and although displaying preferences for PtdIns(3,5)P2, it is capable of hydrolyzing PtdIns(3,4,5)P3 and PtdIns(4,5)P2, at least in vitro. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + phosphate a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + phosphate 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-3,4-bisphosphate) + phosphate H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate Component of the PI(3,5)P2 regulatory complex/PAS complex, at least composed of PIKFYVE, FIG4 and VAC14 (By similarity) (PubMed:19037259). VAC14 nucleates the assembly of the complex and serves as a scaffold by pentamerizing into a star-shaped structure, which can bind a single copy each of PIKFYVE and FIG4 and coordinates their activities (By similarity). Localization requires VAC14 and PIKFYVE. Wide-spread. Defects in Fig4 are the cause of the pale tremor phenotype which is a multi-organ disorder with neuronal degeneration in the central nervous system, peripheral neuronopathy and diluted pigmentation. At postnatal day three (P3), affected homozygotes have diluted pigmentation and reduced size. Intentional tremor develops during the second week after birth, and abnormal limb postures are evident by the third week. There is impaired motor coordination, muscle weakness and 'swimming' gait. There is progressive loss of mobility, reduction in body weight and juvenile lethality.