Has abundant triacylglycerol lipase activity (PubMed:15364929, PubMed:16150821, PubMed:17603008). Transfers fatty acid from triglyceride to retinol, hydrolyzes retinylesters, and generates 1,3-diacylglycerol from triglycerides (PubMed:17603008). Additionally possesses acylglycerol transacylase and phospholipase A2 activities (PubMed:15364929, PubMed:17603008). a triacylglycerol + H2O = a diacylglycerol + a fatty acid + H(+) 2 1-(9Z-octadecenoyl)-glycerol = 1,2-di-(9Z-octadecenoyl)-glycerol + glycerol 1,2-di-(9Z-octadecenoyl)-glycerol + 1-(9Z-octadecenoyl)-glycerol = 1,2,3-tri-(9Z-octadecenoyl)-glycerol + glycerol 1,3-di-(9Z-octadecenoyl)-glycerol + 1-(9Z-octadecenoyl)-glycerol = 1,2,3-tri-(9Z-octadecenoyl)-glycerol + glycerol (9Z)-octadecenoate + 1,2-di-(9Z-octadecenoyl)-glycerol + H(+) = 1,2,3-tri-(9Z-octadecenoyl)-glycerol + H2O 1,2,3-tri-(9Z-octadecenoyl)-glycerol + H2O = (9Z)-octadecenoate + 1,3-di-(9Z-octadecenoyl)-glycerol + H(+) all-trans-retinyl hexadecanoate + H2O = all-trans-retinol + H(+) + hexadecanoate 1,2,3-tri-(9Z-octadecenoyl)-glycerol + all-trans-retinol = all-trans-retinyl 9Z-octadecenoate + di-(9Z)-octadecenoylglycerol a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) The triglyceride lipase activity is inhibited by BEL ((E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one), a suicide substrate inhibitor. Expressed in all tissues examined, including heart, brain, placenta, lung, liver, muscle, kidney, pancreas and spleen. Defects in PNPLA4 may play a role in mitochondrial disorders characterized by complex IV deficiency.