Omega-hydroxyceramide transacylase involved in the synthesis of omega-O-acylceramides (esterified omega-hydroxyacyl-sphingosine; EOS), which are extremely hydrophobic lipids involved in skin barrier formation (PubMed:27751867, PubMed:28248300). Catalyzes the last step of the synthesis of omega-O-acylceramides by transferring linoleic acid from triglycerides to an omega-hydroxyceramide (PubMed:27751867, PubMed:28248300). Omega-O-acylceramides, are required for the biogenesis of lipid lamellae in the stratum corneum and the formation of the cornified lipid envelope which are essential for the epidermis barrier function (PubMed:27751867, PubMed:28248300). These lipids also play a role in keratinocyte differentiation (PubMed:28248300). May also act on omega-hydroxylated ultra-long chain fatty acids (omega-OH ULCFA) and acylglucosylceramides (GlcEOS) (PubMed:28248300). a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(omega-hydroxy-ultra-long chain fatty acyl)-sphingoid base = a diacylglycerol + an N-[omega-(9Z,12Z-octadecadienoyloxy)-O-ultra-long chain fatty acyl]-sphingoid base a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(omega-hydroxy-ultra-long chain fatty acyl)-sphing-4-enine = a diacylglycerol + an N-(omega-(9Z,12Z-octadecadienoyloxy)-ultra-long chain fatty acyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + N-(28-hydroxyoctacosanoyl)-sphing-4-enine = a diacylglycerol + N-(28-(9Z,12Z-octadecadienoyloxy)-octacosanoyl)-sphing-4-enine 1,2,3-tri-(9Z,12Z)-octadecadienoylglycerol + N-(30-hydroxytriacontanoyl)-sphing-4-enine = di-(9Z,12Z)-octadecadienoylglycerol + N-[30-(9Z,12Z-octadecadienoyloxy)-triacontanoyl]-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + N-(32-hydroxydotriacontanoyl)-sphing-4-enine = a diacylglycerol + N-(32-(9Z,12Z-octadecadienoyloxy)-dotricontanoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + N-(32-hydroxydotriacontenoyl)-sphing-4-enine = a diacylglycerol + an N-(32-(9Z,12Z-octadecadienoyloxy)-dotriacontenoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(34-hydroxytetratriacontenoyl)-sphing-4-enine = a diacylglycerol + an N-(34-(9Z,12Z-octadecadienoyloxy)-tetratriacontenoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(34-hydroxytetratriacontadienoyl)-sphing-4-enine = a diacylglycerol + an N-(34-(9Z,12Z-octadecadienoyloxy)-tetratriacontadienoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(36-hydroxyhexatriacontenoyl)-sphing-4-enine = a diacylglycerol + an N-(36-(9Z,12Z-octadecadienoyloxy)-hexatriacontenoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(36-hydroxyhexatriacontadienoyl)-sphing-4-enine = a diacylglycerol + an N-(36-(9Z,12Z-octadecadienoyloxy)-hexatriacontadienoyl)-sphing-4-enine a (9Z,12Z)-octadecadienoyl-containing triacyl-sn-glycerol + an N-(38-hydroxyoctatriacontenoyl)-sphing-4-enine = a diacylglycerol + an N-(38-(9Z,12Z-octadecadienoyloxy)-octatriacontenoyl)-sphing-4-enine Specifically expressed in skin by keratinocytes, at the boundary area between the nucleated stratum granulosum and the denucleated stratum corneum in the epidermis (at protein level) (PubMed:28248300). Also expressed in stomach and other surface lining tissues like intestine and tongue (PubMed:27751867, PubMed:28248300). Also detected in testis as well as in other tissues but at very low level (PubMed:28248300). Up-regulated upon induced differentiation of keratinocytes. Homozygous knockout mice lacking Pnpla1 are obtained at the expected Mendelian ratio but die within 24 hours after birth (PubMed:27751867, PubMed:28248300). They display shiny and taut skin, often with a necrotic tail tip (PubMed:27751867, PubMed:28248300). They are less active, markedly smaller, and weighed significantly less than their wild-type counterpart (PubMed:27751867). Unique linoleate-containing lipids including acylceramides, acylglucosylceramides and (O-acyl)-omega-hydroxy fatty acids are almost absent in the epidermis while there is a reciprocal increase in their putative precursors (PubMed:27751867, PubMed:28248300). The absence of these highly hydrophobic linoleate-containing lipids in the epidermis is responsible for the lethal disruption of the epidermal permeability barrier which is characterized by a decrease in intercellular lipid lamellae in the stratum corneum, the loss or abnormalities of the cornified lipid envelope, and aberrant keratinocyte differentiation (PubMed:27751867, PubMed:28248300). Keratinocyte-specific conditional knockout mice also die shortly after birth, displaying desquamation with alteration of the stratum corneum and of the lipid composition of the epidermis (PubMed:28248300).