Has specific phosphohydrolase activity towards sphingoid base 1-phosphates. Has high phosphohydrolase activity against dihydrosphingosine-1-phosphate and sphingosine-1-phosphate (S1P) in vitro (Probable). 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 (By similarity). Plays a role in the regulation of pancreatic islet beta-cell endoplasmic reticulum stress and proliferation (PubMed:27059959). H2O + sphinganine 1-phosphate = phosphate + sphinganine H2O + sphing-4-enine 1-phosphate = phosphate + sphing-4-enine (4R)-hydroxysphinganine 1-phosphate + H2O = (4R)-hydroxysphinganine + phosphate Highly expressed in pancreatic islets. Expressed in lung, small interstince, colon, kideny and brain. Developmentally regulated. Expression during kidney development increases around 8 fold from 11.5 dpc and adult. Highest expression is found in the ureteric bud. Mutans are viable into the adulthod. They exhibit smaller pancreatic islets, defective beta-cell proliferation and decreased blood insulin levels after treatment with a high-fat diet (PubMed:27059959). Beta-cells show increased expression of proteins characteristic of the endoplasmic reticulum stress response (PubMed:27059959). Belongs to the type 2 lipid phosphate phosphatase family.