The function of ENSG00000104763 (ASAH1, N-acylsphingosine amidohydrolase 1) is as follows. Lysosomal ceramidase that hydrolyzes sphingolipid ceramides into sphingosine and free fatty acids at acidic pH (PubMed:10610716, PubMed:11451951, PubMed:15655246, PubMed:26898341, PubMed:36752535, PubMed:7744740, PubMed:7852294). 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:10610716). Has a higher catalytic efficiency towards C12- ceramides versus other ceramides (PubMed:15655246, PubMed:7744740). Also catalyzes the reverse reaction allowing the synthesis of ceramides from fatty acids and sphingosine (PubMed:12764132, PubMed:12815059). For the reverse synthetic reaction, the natural sphingosine D-erythro isomer is more efficiently utilized as a substrate compared to D- erythro-dihydrosphingosine and D-erythro-phytosphingosine, while the fatty acids with chain lengths of 12 or 14 carbons are the most efficiently used (PubMed:12764132). Also has an N-acylethanolamine hydrolase activity (PubMed:15655246). By regulating the levels of ceramides, sphingosine and sphingosine-1-phosphate in the epidermis, mediates the calcium-induced differentiation of epidermal keratinocytes (PubMed:17713573). Also indirectly regulates tumor necrosis factor/TNF- induced apoptosis (By similarity). By regulating the intracellular balance between ceramides and sphingosine, in adrenocortical cells, probably also acts as a regulator of steroidogenesis (PubMed:22261821). {ECO:0000250|UniProtKB:Q9WV54, ECO:0000269|PubMed:10610716, ECO:0000269|PubMed:11451951, ECO:0000269|PubMed:12764132, ECO:0000269|PubMed:12815059, ECO:0000269|PubMed:15655246, ECO:0000269|PubMed:17713573, ECO:0000269|PubMed:22261821, ECO:0000269|PubMed:26898341, ECO:0000269|PubMed:36752535, ECO:0000269|PubMed:7744740, ECO:0000269|PubMed:7852294, ECO:0000303|PubMed:10610716}. [Isoform 2]: May directly regulate steroidogenesis by binding the nuclear receptor NR5A1 and negatively regulating its transcriptional activity. .