Degrades bioactive fatty acid amides to their corresponding acids, with the following preference: N-palmitoylethanolamine > N-myristoylethanolamine > N-lauroylethanolamine = N-stearoylethanolamine > N-arachidonoylethanolamine > N-oleoylethanolamine (PubMed:15655246, PubMed:17980170, PubMed:18793752, PubMed:30301806, PubMed:22825852). Also exhibits weak hydrolytic activity against the ceramides N-lauroylsphingosine and N-palmitoylsphingosine (PubMed:15655246). H2O + N-(long-chain fatty acyl)ethanolamine = a long-chain fatty acid + ethanolamine H2O + N-hexadecanoylethanolamine = ethanolamine + hexadecanoate H2O + N-dodecanoylethanolamine = dodecanoate + ethanolamine H2O + N-tetradecanoylethanolamine = ethanolamine + tetradecanoate an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine H2O + N-hexadecanoylsphing-4-enine = hexadecanoate + sphing-4-enine H2O + N-dodecanoylsphing-4-enine = dodecanoate + sphing-4-enine Stimulated by DTT and Nonidet P-40. Optimum pH is 4.5 with N-palmitoylethanolamine as substrate. Lipid metabolism; fatty acid metabolism. Heterodimer of an alpha and a beta subunit, produced by autocatalytic cleavage. Expressed in numerous tissues, with highest levels in liver and kidney, followed by pancreas. N-glycosylated (PubMed:17980170, PubMed:18793752, PubMed:30301806). Tunicamycin treatment causes a reduction in specific activity against N-palmitoylethanolamine. A disulfide bond is seen in the crystal structure of the human protein, but the Cys residues are not conserved in rodents. Autoproteolytic cleavage at pH 4.5 gives rise to the alpha and beta subunit (PubMed:15655246, PubMed:22040171, PubMed:17980170, PubMed:18793752, PubMed:30301806). Cleavage gives rise to a conformation change that activates the enzyme (PubMed:17980170, PubMed:18793752, PubMed:30301806, PubMed:22040171). The same catalytic Cys residue mediates the autoproteolytic cleavage and subsequent hydrolysis of lipid substrates (PubMed:17980170, PubMed:18793752) (Probable). Belongs to the acid ceramidase family.