Canadian Medical Guide > Chemicals and Drugs > Amino Acids, Peptides, and Proteins > Proteins > Apoproteins > Apolipoproteins Terms and Definitions
Apolipoproteins
Medical Definition: | The protein components of lipoproteins which remain after the lipids to which the proteins are bound have been removed. They play an important role in lipid transport and metabolism. |
Guide Notes: | /biosyn /drug eff /physiol /ultrastruct permitted |
Previously Indexed: | Apoproteins (1972-1976),Lipoproteins (1966-1976),specific lipoprotein (1972-1976) |
Apolipoproteins A - Lipoproteins found in human blood serum in the high-density and very-high-density lipoprotein fraction (HDL; VHDL). They consist of several different polypeptides, the most important of which are apolipoprotein A-I and A-II. They maintain the structural integrity of the HDL particles and are activators of lecithin:cholesterol acyltransferase (LCAT). Atherosclerotic patients show low apolipoprotein A levels and these apolipoproteins are either absent or present in extremely low plasma concentration in TANGIER DISEASE. | |
Apolipoproteins B - Structural proteins of chylomicrons, VLDL; and LDL. They are important in the secretion and transport of these LIPOPROTEINS and function as recognition signals for binding and internalization of LDL particles by the LDL receptor (RECEPTORS, LDL). Atherosclerotic patients show high levels of Apo-B in the blood while in the case of ABETALIPOPROTEINEMIA they are not detectable in serum. | |
Apolipoproteins C - Lipoproteins located on the surface of VLDL. They are transferred to HDL throughout the catabolism of VLDL and affect lipoprotein lipase activity. A genetic lack of Apo C-II results in hyperglyceridemia and low levels of HDL. Another form of hyperglyceridemia with normal Apo C-II levels is caused by a high concentration of Apo C-III in VLDL. | |
Apolipoproteins E - Prominent protein constituents of plasma VLDL, chylomicrons, and a subfraction of HDL as well as of remnant lipoproteins which are derived from the lipoprotein lipase-mediated intravascular catabolism of triglyceride-rich lipoproteins. Apolipoproteins E are recognized by the LDL receptor and Apo E receptor. Any defect in the Apo E metabolism leads to increased plasma Apo E levels. A strong association has been found between high levels of Apo E and type III hyperlipoproteinemia. |
Apolipoproteins Medical Definitions and Terms
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