The binding of lipids (soluble oil molecules) and cholesterol to Apoliproteins result in the formation of lipoproteins which carry lipids through the circulatory and lymphatic organs. The Apo A1 is the major protein component of high-density lipoprotein (HDL). Deficiency of APOA1 is related with HDL deficiencies and is involved in protection against Alzheimer.APOA and APOAE cooperate to adjust the levels of triglyceride in coronary heart disease.
6 main classes of apolipoproteins are APOA, APOB, APOC, APOD, APOE and APOH. APOA1 takes an important role in the return of surplus cholesterol from peripheral tissues to the liver. Lipoprotein lipid molecules are precipitate in water thus being insoluble. Nevertheless, due to of their amphipathic/detergent like characteristics, Apolipoproteins fence in the lipids, forming a lipoprotein particle which is soluble in water, hence travel in blood. The successful transport of dietary and endogenous lipids to peripheral tissues which are used as an energy source is due to APOB and APOE Apolipoprtoeins. APOE is primarily located in HDL and VLDL Apolipoproteins act as lipid transfer carrier enzymes, cofactors and receptor ligands which control lipoprotein metabolism.
Apolipoproteins are composed from various lipoproteins such as exchangeable Apolipoprtoeins and non-exchangeable. An example of non-exchangeable apolipoprotein is APOAB which is attached to the lipoprotein particle while examples of Lipoprotein exchangeable are APOM, APOD, APOJ, APOH and APOA1 which are transported between different lipoprotein molecules. APOB and APOA1 are the main protein components of LDL and HDL. APOB can be found in 2 formations, 2% APOB-48 and 98% APOB-100. APOB-48 is formed in the intestine and APOB-100 is formed in the liver, fused to LDL and regulates ligand–receptor uptake of LDL circulate in its free form.