Apolipoprotein AII (Apo A2), the second most abundant protein after Apo A1 of human plasma high-density lipoproteins (HDL), is the most lipophilic of the exchangeable apolipoproteins. Apo A2 is synthesized by the liver and the small intestine and found in plasma as a monomer, dimer. The Apo A2 gene consists of 4 exons and 3 introns. The four exons encode the 5′ untranslated region, pre peptide, a short N terminal domain and a C terminal domain composed of a variable number of lipid binding amphipathic helices.
Apo A2 may stabilize HDL structure by its association with lipids, and affect the HDL metabolism. Role of Apo A2 in lipid metabolism and atherosclerosis show important clinical significance. Apo A2 levels have been associated with increased susceptibility to atherosclerosis, increased free fatty acid levels, increased body fat, and increased insulin resistance.