Apolipoprotein B, Human Plasma

Apolipoprotein B is the dominant protein constituent of LDL. The concentration of Apo B in normal plasma is 90 mg per 100 ml. Apo B is thought to stabilize lipid emulsions, serve as a cofactor and modulator of enzymatic reactions, manage export of lipids out of cells and direct lipids to target organs. Apo B levels are positively correlated with the risk of coronary disease. Apo B levels may be a more sensitive predictor of cardiovascular risk than LDL levels and do not involve fasting for accurate measurement. Two forms of Apo B exist: Apo B-100 and Apo B-48. The first is found in VLDL and LDL and is produced by the liver. The second is found in chylomicrons and originates in the intestine. Mutations in this gene or its regulatory region cause hypobetalipoproteinemia, normotriglyceridemic and hypercholesterolemia due to ligand-defective apoB, diseases affecting plasma cholesterol and apoB levels.