ApoE belongs to a group of proteins that bind reversibly with lipoprotein and play an important role in lipid metabolism. ApoE is an important constituent of all plasma lipoproteins. It’s interaction with specific ApoE receptor enables uptake of chylomicron remnants by liver cells, which is an essential step during normal lipid metabolism. It also binds with the LDL receptor (apo B/E). Defects in ApoE are a cause of hyperlipoproteinemia type III. ApoE exists in three major isoforms; E2, E3, and E4, which differ from one another by a single amino-acid substitution. E3 is the most common isoform and is present in 40-90% of the population.