FunctionMinor apolipoprotein mainly associated with HDL and to a lesser extent with VLDL. May also be associated with chylomicrons. Important determinant of plasma triglyceride (TG) levels by both being a potent stimulator of apo-CII lipoprotein lipase (LPL) TG hydrolysis and a inhibitor of the hepatic VLDL-TG production rate (without affecting the VLDL-apoB production rate) (By similarity). Activates poorly lecithin:cholesterol acyltransferase (LCAT) and does not enhance efflux of cholesterol from macrophages.
Tissue specificityLiver and plasma.
Involvement in diseaseDefects in APOA5 are a cause of susceptibility to familial hypertriglyceridemia (FHTR)[MIM:145750].mFamilial hypertriglyceridemia is a common inherited disorder in which the concentration of very low density lipoprotein (VLDL) is elevated in the plasma. This leads to increased risk of heart disease, obesity, and pancreatitis. Defects in APOA5 are a cause of hyperlipoproteinemia type 5 (HLPP5) [MIM:144650]. HLPP5 is characterized by increased amounts of chylomicrons and very low density lipoprotein (VLDL) and decreased low density lipoprotein (LDL) and high density lipoprotein (HDL) in the plasma after a fast. Numerous conditions cause this phenotype, including insulin-dependent diabetes mellitus, contraceptive steroids, alcohol abuse, and glycogen storage disease type 1A (GSD1A) [MIM:232200].
Sequence similaritiesBelongs to the apolipoprotein A1/A4/E family.
Post-translational modificationsPhosphorylation sites are present in the extracelllular medium.