– Apolipoprotein A-II(Apo-AII for short), also known as Apolipoprotein A2, is a secreted protein which belongs to the apolipoprotein A2 family. It exists as a disulfide-linked homodimer; and also can form a disulfide-linked heterodimer with APOD. APOA2 is the 2nd most abundant protein of the high density lipoprotein particles. This protein may stabilize HDL (high density lipoprotein) structure by its association with lipids, and affect the HDL metabolism. Defects in APOA2 gene might cause apolipoprotein A-II deficiency or hypercholesterolemia.