Golgi ceramidase that catalyzes the hydrolysis of ceramides into sphingoid bases like sphingosine and free fatty acids at alkaline pH (PubMed:29401619). 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:29401619). Has a better catalytic efficiency towards unsaturated long-chain ceramides, including C18:1-, C20:1- and C24:1-ceramides (By similarity) (PubMed:29401619). Saturated long-chain ceramides and unsaturated very long-chain ceramides are also good substrates, whereas saturated very long-chain ceramides and short-chain ceramides are poor substrates. Also hydrolyzes dihydroceramides to produce dihydrosphingosine (By similarity). It is the ceramidase that controls the levels of circulating sphingosine-1-phosphate and dihydrosphingosine-1-phosphate in plasma through their production by hematopoietic cells (PubMed:29401619). Regulates cell proliferation, autophagy and apoptosis by the production of sphingosine and sphingosine-1-phosphate. As part of a p53/TP53-dependent pathway, promotes for instance autophagy and apoptosis in response to DNA damage. Through the production of sphingosine, may also regulate the function of the Golgi complex and regulate the glycosylation of proteins (By similarity). an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine H2O + N-(15Z-tetracosenoyl)-sphing-4-enine = (15Z)-tetracosenoate + sphing-4-enine H2O + N-eicosanoyl-sphing-4-enine = eicosanoate + sphing-4-enine H2O + N-octadecanoylsphing-4-enine = octadecanoate + sphing-4-enine H2O + N-hexadecanoylsphing-4-enine = hexadecanoate + sphing-4-enine H2O + N-tetradecanoylsphing-4-enine = sphing-4-enine + tetradecanoate H2O + N-dodecanoylsphing-4-enine = dodecanoate + sphing-4-enine H2O + N-tetracosanoyl-sphing-4-enine = sphing-4-enine + tetracosanoate H2O + N-(hexanoyl)sphing-4-enine = hexanoate + sphing-4-enine H2O + N-(9Z-octadecenoyl)-sphing-4-enine = (9Z)-octadecenoate + sphing-4-enine an N-acylsphinganine + H2O = a fatty acid + sphinganine Lipid metabolism; sphingolipid metabolism. Widely expressed with higher expression in lung. Homozygous knockout mice display no overt phenotype (PubMed:29401619). Reduced levels of sphingosine, dihydrosphingosine, sphingosine-1-phosphate and dihydrosphingosine -1-phosphate are observed in plasma, erythrocytes and platelets (PubMed:29401619). Belongs to the alkaline ceramidase family. Chimera.