At least 9 distinct polymorphic forms of apolipoproteins are known. The apolipoproteins act as stabilizers of the intact lipoprotein particles. Quantitative measurements of HDL, LDL and VLDL particles in human serum are often used to estimate an individuals' relative risk of coronary heart disease. In addition, quantitative immunological measurements of certain apolipoproteins (especially A-1 and B) have been suggested to be more accurate estimators of coronary heart disease than measurements of lipoprotein particles (especially HDL and LDL).
Apolipoprotein C-II (apoCII) is in found in chylomicrons (large lipoprotein particles absorbed from the gastrointestinal tract) and VLDL (large lipoproteins that are broken down to eventually form LDL). ApoCII activates the enzyme lipoprotein lipase, which hydrolyzes triglycerides and thus provides free fatty acids for cells.
Dernick G et al. Multidimensional profiling of plasma lipoproteins by size exclusion chromatography followed by reverse-phase protein arrays. J Lipid Res52:2323-31 (2011).
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