Endoplasmic reticulum and Golgi ceramidase that catalyzes the hydrolysis of unsaturated long-chain C18:1-, C20:1- and C20:4-ceramides, dihydroceramides and phytoceramides into sphingoid bases like sphingosine and free fatty acids at alkaline pH (PubMed:20068046, PubMed:26792856, PubMed:20207939, PubMed:11356846, PubMed:30575723). Ceramides, sphingosine, and its phosphorylated form sphingosine-1-phosphate are bioactive lipids that mediate cellular signaling pathways regulating several biological processes including cell proliferation, apoptosis and differentiation (PubMed:20068046). Controls the generation of sphingosine in erythrocytes, and thereby sphingosine-1-phosphate in plasma (PubMed:20207939). Through the regulation of ceramides and sphingosine-1-phosphate homeostasis in the brain may play a role in neurons survival and function (By similarity). By regulating the levels of pro-inflammatory ceramides in immune cells and tissues, may modulate the inflammatory response (By similarity). an N-acyl-(4R)-4-hydroxysphinganine + H2O = (4R)-hydroxysphinganine + a fatty acid H2O + N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sphing-4-enine = (5Z,8Z,11Z,14Z)-eicosatetraenoate + sphing-4-enine H2O + N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sphinganine = (5Z,8Z,11Z,14Z)-eicosatetraenoate + sphinganine H2O + N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-(4R)-hydroxysphinganine = (4R)-hydroxysphinganine + (5Z,8Z,11Z,14Z)-eicosatetraenoate H2O + N-(11Z-eicosenoyl)-sphing-4-enine = (11Z)-eicosenoate + sphing-4-enine H2O + N-(11Z-eicosenoyl)-sphinganine = (11Z)-eicosenoate + sphinganine H2O + N-(11Z-eicosenoyl)-(4R)-hydroxysphinganine = (11Z)-eicosenoate + (4R)-hydroxysphinganine H2O + N-(9Z-octadecenoyl)-sphing-4-enine = (9Z)-octadecenoate + sphing-4-enine H2O + N-(9Z-octadecenoyl)-sphinganine = (9Z)-octadecenoate + sphinganine H2O + N-(9Z-octadecenoyl)-(4R)-hydroxysphinganine = (4R)-hydroxysphinganine + (9Z)-octadecenoate an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine an N-acylsphinganine + H2O = a fatty acid + sphinganine Activated by 5 mM Ca(2+) and inhibited by 5 mM Zn(2+). Optimum pH is 9.5. Lipid metabolism; sphingolipid metabolism. Ubiquitously expressed. Highly expressed in placenta (PubMed:11356846). Expressed in erythrocytes (PubMed:20207939). The disease is caused by variants affecting the gene represented in this entry. Belongs to the alkaline ceramidase family.