LIPO PROTEIN METABOLISM : LIPO PROTEIN METABOLISM Dr. V. Siva Prabodh MD
Dept. of Biochemistry
NRI Medical College Lipoproteins : Lipoproteins These are molecular complexes which contains Lipids & proteins
Function: Transports Lipids in blood.
Classification of Lipoproteins
Five Major classes
FFA with albumin Lipo proteins are seperated by Ultra centrifugation/Electrophoresis : Lipo proteins are seperated by Ultra centrifugation/Electrophoresis Slide 4: Chylomicrons: Synthesized in the Intestine.
Transport Exogenous lipids (Dietary Lipids)
99% Lipids, 1% protein, Density very less.
2) VLDL : Produced in the Liver & Intestine Transport Endogenous lipids Slide 5: 3) LDL : Formed from VLDL in blood Transport cholesterol from Liver to other tissues.
4) HDL : Mostly synthesized in Liver
Transport cholesterol from peripheral tissues to Liver (Reverse cholesterol transport)
5) FFA with albumin: Each molecule of albumin hold 20-30 molecules of FFA. Apoproteins : Apoproteins The protein forms of Lipoproteins are known as Apolipoproteins or Apoproteins.
Structural component – apo A, apo B, apo B100 apo C
Recognizes surface receptors – apo E, apo B100
Activate Lipoprotein Lipase – apo C II LDL : LDL Low density Lipoprotein is formed from VLDL and the Intermediate is IDL.
LDL contain high cholesterol and less TAG.
Function:– Supply cholesterol to extra hepatic tissues.
LDL particles bind to specific receptors over the cell membrane which are clathrin coated pit
Apo B100 recognizes the receptors over the cell membrane
Deficiency of LDL receptors leads to Increased circulating LDL and hence cholesterol increases
Eg: Type IIa hyperbeta lipoproteinemia. HDL : HDL High density Lipoproteins (Three types HDL1, HDL2, HDL3)
Cholesterol is transported from Extra hepatic tissue to Liver where it is excreted in the form of bile.
Anti – atherogenic, Good cholesterol
Intestinal cells synthesize HDL and release into blood.
LCAT: Lecithin cholesterol Acyl transferases, transfer PUFA from Lecithin to cholesterol to form cholesterol ester, which moves into interior of HDL
APO A I activates LCAT
The HDL with more cholesterol are taken up by Liver cells, and cholesterol is released into Liver. (Reverse cholesterol transport) HYPER LIPOPROTEINEMIAS : HYPER LIPOPROTEINEMIAS Slide 11: Familial hypercholesterolemia (type II a) Slide 13: Thank you