Mediates the transfer of phospholipids and free cholesterol from triglyceride-rich lipoproteins (low density lipoproteins or LDL and very low density lipoproteins or VLDL) into high-density lipoproteins (HDL) as well as the exchange of phospholipids between triglyceride-rich lipoproteins themselves (PubMed:7654777, PubMed:7615508, PubMed:10079112,). Facilitates the transfer of a spectrum of different lipid molecules, including sphingomyelin, phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and phosphatidyl ethanolamine (PubMed:10079112). Plays an important role in HDL remodeling which involves modulating the size and composition of HDL (By similarity). Also plays a key role in the uptake of cholesterol from peripheral cells and tissues that is subsequently transported to the liver for degradation and excretion (By similarity). Two distinct forms of PLTP exist in plasma: an active form that can transfer phosphatidylcholine from phospholipid vesicles to HDL, and an inactive form that lacks this capability (By similarity). a 1,2-diacyl-sn-glycero-3-phosphocholine(in) = a 1,2-diacyl-sn-glycero-3-phosphocholine(out) a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(in) = a 1,2-diacyl-sn-glycero-3-phosphoethanolamine(out) a 1,2-diacyl-sn-glycerol(in) = a 1,2-diacyl-sn-glycerol(out) a 1,2-diacyl-sn-glycero-3-phosphate(in) = a 1,2-diacyl-sn-glycero-3-phosphate(out) a sphingomyelin(in) = a sphingomyelin(out) 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol)(in) = 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol)(out) a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol)(in) = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol)(out) 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphoethanolamine(in) = 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphoethanolamine(out) N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine(in) = N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine(out) 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine(in) = 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine(out) Nuclear export is XPO1/CRM1-dependent. Highest level expression in the lung, brain and heart with relatively low levels in the liver, skeletal muscle and testis and very low levels found in the spleen and kidney. Glycosylation is necessary for secretion and its phospholipid transfer activity. Mice show a complete loss of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and sphingomyelin transfer activities, and a partial loss of free cholesterol transfer activity (PubMed:10079112). Transfer of VLDL phospholipid into HDL is abolished (PubMed:10079112). A marked reduction in the levels of plasma HDL phospholipid, cholesteryl ester and free cholesterol seen, whereas the levels of non-HDL lipids are not significantly altered (PubMed:10079112). Belongs to the BPI/LBP/Plunc superfamily. BPI/LBP family.