Has specific phosphohydrolase activity towards sphingoid base 1-phosphates. Has high phosphohydrolase activity against dihydrosphingosine-1-phosphate and sphingosine-1-phosphate (S1P) in vitro (PubMed:12411432). Sphingosine-1-phosphate phosphatase activity is needed for efficient recycling of sphingosine into the sphingolipid synthesis pathway (By similarity). May play a role in attenuating intracellular sphingosine 1-phosphate (S1P) signaling. May play a role in pro-inflammatory signaling (PubMed:17113265). Plays a role in the regulation of pancreatic islet beta-cell endoplasmic reticulum stress and proliferation (By similarity). H2O + sphinganine 1-phosphate = phosphate + sphinganine H2O + sphing-4-enine 1-phosphate = phosphate + sphing-4-enine (4R)-hydroxysphinganine 1-phosphate + H2O = (4R)-hydroxysphinganine + phosphate Expressed strongly in kidney and heart, followed by brain, colon, small intestine and lung. Not detected in skeletal muscle, thymus, spleen, liver, placenta, and peripheral blood leukocytes. Strongly induced by TNF, also induced by bacterial lipopolycaccharides (LPS) in neutrophils, endothelial cells, and other cell types. Not induced by growth-related factors. Belongs to the type 2 lipid phosphate phosphatase family.