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What is LCAT is activated by? and explain in detail?
Ans. A. Apo AI. (Ref Harper Biochemistry 26th/48, 206; Harrison 17th/pg. 2417; 18th/Table 356-2 c)Apolipo- proteinFunctionChylomicronChylomicron remnantVLDLIDLLDL HDLEMediates remnant uptake A-IActivates LCAT C-IILipoprotein lipase cofactor B-48Mediates chylomicron secretion B-100Binds LDL receptor APOLIPOPROTEINSApo-AI, A-II, A-IVfound in HDL and chylomicronsApo-AI, AII, AIVfound primarily on HDLApo-AI and AIIsynthesized in liver and intestineApo-A IVsynthesized in intestine only.Apo-AIcomprises 70-80% protein of HDL AII: is second most abundant in HDLApo-AILCAT activator and inversely related to CHDB-100Binds to LDL receptor, mediates VLDL secretionB-48mainly Mediates chylomicron secretionC-IICofactor for lipoprotein lipase.EMediates Extra (remnant) uptakeMajor ApolipoproteinsApolipoproteinPrimary SourceLipoprotein AssociationFunctionApoA-IIntestine, liverHDL, chylomicronsStructural protein for HDL Activates LCATApoA-IILiverHDL, chylomicronsStructural protein for HDLApoA-IVIntestineHDL, chylomicronsUnknownApoA-VLiverVLDL, chylomicronsPromotes LPL-mediated triglyceride lipolysisApo(a)LiverLp(a)UnknownApoB-48IntestineChylomicronsStructural protein for chylomicronsApoB-100LiverVLDL, IDL, LDL, Lp(a)Structural protein for VLDL, LDL, IDL, Lp(a)Ligand for binding to LDL receptorApoC-ILiverChylomicrons, VLDL, HDLUnknownApoC-IILiverChylomicrons, VLDL, HDLCofactor for LPLApoC-IIILiverChylomicrons, VLDL, HDLInhibits lipoprotein binding to receptorsApoELiverChylomicron remnants, IDL, HDLLigand for binding to LDL receptorApoHLiverChylomicrons, VLDL, LDL, HDLB2 glycoprotein IApoJLiverHDLUnknownApoLUnknownHDLUnknownApoMLiverHDLUnknownEducational points:Fredrickson Classification of HyperlipoproteinemiasPhenotypeIIIaIIbIIIIVVLipoprotein, elevatedChylomicronsLDLLDL and VLDLChylomicron and VLDL remnantsVLDLChylomicrons and VLDLTriglycerides N Cholesterol (total) N/ LDL-cholesterol HDL-cholesterol N/ N Plasma appearanceLactescentClearClearTurbidTurbidLactescentXanthomasEruptiveTendon,NonePalmar,NoneEruptive tuberous tuberoeruptive Pancreatitis+++0000+++Coronary atherosclerosis0++++++++++/-+/-Peripheral atherosclerosis0+++++/-+/-Molecular defectsLPL and ApoC-HLDL receptor, ApoEApoA-VApoA-V and ApoB-100,PCSK9, LDLRAP, ABCG5 and ABCG8 GPIHBP1Genetic nomenclatureFCSFH, FDB,ADH, ARH, sitosterolemiaFCHLFDBLFHTGFHTG