Plasma membrane ceramidase that hydrolyzes sphingolipid ceramides into sphingosine and free fatty acids at neutral pH (PubMed:15271994). 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. Also catalyzes the reverse reaction allowing the synthesis of ceramides from fatty acids and sphingosine. Together with sphingomyelinase, participates in the production of sphingosine and sphingosine-1-phosphate from the degradation of sphingomyelin, a sphingolipid enriched in the plasma membrane of cells (By similarity). Also participates in the hydrolysis of ceramides from the extracellular milieu allowing the production of sphingosine-1-phosphate inside and outside cells (By similarity). an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine H2O + N-dodecanoylsphing-4-enine = dodecanoate + sphing-4-enine Binds 1 zinc ion per subunit. Optimum pH is 7.5 for N-dodecanoylsphing-4-enine hydrolysis. Lipid metabolism; sphingolipid metabolism. Detected in intestine (at protein level). Expressed and active during embryonic development. N-glycosylated. O-glycosylated. Fishes display severe embryonic morphological and cellular abnormalities such as abnormal morphogenesis in the head and tail, pericardial edema, defect of blood cell circulation, and an increase of apoptotic cells, especially in the head and neural tube regions, at 36 hours post-fertilization. Belongs to the neutral ceramidase family.