Catalyzes the cleavage of the N-acyl linkage of the ceramides (Cers) to yield sphingosine (Sph) and free fatty acid. Also catalyzes the synthesis of Cers from Sph and fatty acid. Cers containning C6-C24 fatty acids are well hydrolyzed, and Cers with mono unsaturated fatty acids are much more hydrolyzed than those with saturated fatty acids. an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine an N-acylsphinganine + H2O = a fatty acid + sphinganine an N-acyl-(4R)-4-hydroxysphinganine + H2O = (4R)-hydroxysphinganine + a fatty acid H2O + N-(9Z-octadecenoyl)-sphing-4-enine = (9Z)-octadecenoate + sphing-4-enine H2O + N-(hexanoyl)sphing-4-enine = hexanoate + sphing-4-enine H2O + N-hexadecanoylsphing-4-enine = hexadecanoate + sphing-4-enine H2O + N-octadecanoylsphing-4-enine = octadecanoate + sphing-4-enine H2O + N-eicosanoyl-sphing-4-enine = eicosanoate + sphing-4-enine H2O + N-(15Z-tetracosenoyl)-sphing-4-enine = (15Z)-tetracosenoate + sphing-4-enine H2O + N-tetracosanoyl-sphing-4-enine = sphing-4-enine + tetracosanoate Binds 1 zinc ion per subunit. 90% of activity is inhibited by nickel, zinc and calcium ions. Magnesium, cobalt, copper and manganese ions inhibit between 50 and 80% of activity. Optimum pH is between 8 and 9. 10 minutes at 100 degrees Celsius abolishes completely the activity. Belongs to the neutral ceramidase family.