Apolipoprotein AI

Apolipoprotein AI (Apo AI) is a protein that plays a crucial role in the metabolism of lipids in the body. It is the primary protein component of high density lipoprotein (HDL) in the blood and aids in the transport of cholesterol to the liver for excretion or re-utilization.

Structure

Apo AI is a 28.1 kDa protein composed of 243 amino acids. It is synthesized in the liver and small intestine and forms a specific type of lipoprotein particle, HDL, in plasma. The structure of Apo AI is characterized by a series of amphipathic alpha-helices, which are suitable for lipid binding.

Function

The primary function of Apo AI is to participate in the reverse cholesterol transport pathway, where it helps to transport cholesterol from tissues back to the liver. It does this by binding to phospholipids and cholesterol to form HDL particles, which are then transported back to the liver for excretion or re-utilization. Apo AI is also involved in the activation of Lecithin-cholesterol acyltransferase (LCAT), an enzyme that is important in the maturation of HDL particles.

Clinical significance

Alterations in the normal concentration of Apo AI in the blood can lead to health problems. Low levels of Apo AI have been associated with an increased risk of coronary artery disease due to the role of Apo AI in HDL formation and cholesterol transport. Conversely, high levels of Apo AI can be protective against atherosclerosis.

Research

Research into Apo AI has focused on its potential use in the treatment of cardiovascular disease. Synthetic HDL particles made from Apo AI have been used in clinical trials to test their efficacy in reducing plaque in coronary arteries.

See also

• Apolipoprotein
• High-density lipoprotein
• Lecithin-cholesterol acyltransferase
• Coronary artery disease