The function of ACER3 (alkaline ceramidase 3, Ensembl gene identifier ENSG00000078124) is as follows. Endoplasmic reticulum and Golgi ceramidase that catalyzes the hydrolysis of unsaturated long-chain C18:1-, C20:1- and C20:4- ceramides, dihydroceramides and phytoceramides into sphingoid bases like sphingosine and free fatty acids at alkaline pH (PubMed:11356846, PubMed:20068046, PubMed:20207939, PubMed:26792856, PubMed:30575723). 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:20068046). Controls the generation of sphingosine in erythrocytes, and thereby sphingosine-1- phosphate in plasma (PubMed:20207939). Through the regulation of ceramides and sphingosine-1-phosphate homeostasis in the brain may play a role in neurons survival and function (By similarity). By regulating the levels of pro-inflammatory ceramides in immune cells and tissues, may modulate the inflammatory response (By similarity). {ECO:0000250|UniProtKB:Q9D099, ECO:0000269|PubMed:11356846, ECO:0000269|PubMed:20068046, ECO:0000269|PubMed:20207939, ECO:0000269|PubMed:26792856, ECO:0000269|PubMed:30575723, ECO:0000303|PubMed:20068046}.