The function of SLC27A4 (solute carrier family 27 member 4, Ensembl gene identifier ENSG00000167114) is as follows. Mediates the levels of long-chain fatty acids (LCFA) in the cell by facilitating their transport across cell membranes (PubMed:10518211, PubMed:12556534, PubMed:20448275, PubMed:21395585, PubMed:22022213). Appears to be the principal fatty acid transporter in small intestinal enterocytes (PubMed:20448275). Also functions as an acyl-CoA ligase catalyzing the ATP-dependent formation of fatty acyl- CoA using LCFA and very-long-chain fatty acids (VLCFA) as substrates, which prevents fatty acid efflux from cells and might drive more fatty acid uptake (PubMed:22022213, PubMed:24269233). Plays a role in the formation of the epidermal barrier. Required for fat absorption in early embryogenesis (By similarity). Probably involved in fatty acid transport across the blood barrier (PubMed:21395585). Indirectly inhibits RPE65 via substrate competition and via production of VLCFA derivatives like lignoceroyl-CoA. Prevents light-induced degeneration of rods and cones (By similarity). {ECO:0000250|UniProtKB:Q91VE0, ECO:0000269|PubMed:10518211, ECO:0000269|PubMed:12556534, ECO:0000269|PubMed:20448275, ECO:0000269|PubMed:21395585, ECO:0000269|PubMed:22022213, ECO:0000269|PubMed:24269233}.