What are lipoproteins? Structure of lipoprotein complex. Classification of lipoproteins. Important enzyme and protein involved in lipoprotein metabolism. Apolipoprotein. Lipoprotein metabolism. Clinical disorders Importance of lipoprotein. Conclusion Reference.

1. By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPOSIS
• What are lipoproteins?
• Structure of lipoprotein complex.
• Classification of lipoproteins.
• Important enzyme and protein involved in lipoprotein
metabolism.
• Apolipoprotein.
• Lipoprotein metabolism.
• Clinical disorders
• Importance of lipoprotein.
• Conclusion
• Reference.

3. WHAT ARE LIPOPROTEINS?
• Lipoprotein are a handful of different molecules that interact
with water insoluble molecules, and transports those fats in
the plasma.
• Lipoprotein are conjugated proteins; lipid are the prosthetic
group and lipid- free protein are designated as apolipoprotein
or apoprotein.
• The textbook describes the lipoprotein as “ oil tanker”

5. Hydrophobic lipids
Amphiphilic lipids

6. APOLIPOPROTEIN
• OUTER PROTEIN “SHELL” of the lipoprotein molecules.

7. • Apo AI: Activator LCAT
• Apo AII: Inhibitor of hepatic lipase (HL)
• Apo A-IV: Activator of LCAT
• Apo B-100 (liver, 4564 Aa): structure, ligand
• Apo B-48 (intestine, 2152Aa): structure
• Apo C-I : Activator of LCAT
• Apo C-II: Activator of LPL
• Apo C-III: Inhibitor of LPL
• Apo D: Function unknown
• Apo E: Ligand

8. STRUCTURE OF LIPOPROTEIN

9. STRUCTURE OF LIPOPROTEIN

10. CLASSIFICATION
Classification of plasma lipoproteins
according to their density
• Chylomicron (CM)
• Very low density lipoprotein (VLDL)
• Intermediate density lipoprotein (IDL)
• Low density lipoprotein (LDL)
• High density lipoprotein (HDL)

11. • Each contains different
kinds and amounts of
lipids and proteins
– The more protein,
the higher the
density
– The more lipid, the
lower the density
• Each has different
function
Lipoproteins

12. CM VLDL LDL HDL
Density (g/mL) <0.96 0.96-1.006 1.006-1.063 1.063-1.21
Diameter (nm) 100-1000 30-90 20-25 10-20
Apolipoprotein A,C,E,B48 A,C,E,B100 B100 A,C,D,E
Composition (%)
Proteins 2 10 20 40
Lipids 98 90 80 60
Lipid composition (%)
TG 88 55 12 12
CE+C 4 24 59 40
PL 8 20 28 47
Free fatty acid - 1 1 1
Characteristics of human plasma lipoproteins

13. a-lipoprotein (HDL)
Pre-b-lipoprotein (VLDL)
b-lipoprotein (LDL)
CM
Classification of plasma lipoproteins according to
their electrophoretic mobility

14. ENZYMES
• Locate in extracellular on the walls of
– blood capillaries, anchored to the endothelium.
• Hydrolyze triglyceride (TG) in the core of
– CM and VLDL to free fatty acids and glycerol.
• The free fatty acids are transported into the
– tissue, mainly adipose, heart, and muscle (80%),
– while about 20% goes indirectly to the liver.
LPL (Lipoprotein Lipase)

16. • Bound to the surface of liver cells,
• Hydrolyzes TG to free fatty acids and glycerol
• Unlike LPL, HL does not react readily with
• CM or VLDL but is concerned with TG
• hydrolysis in VLDL remnants and HDL metabolism
HL
(Hepatic Lipase)

17. LCAT
(Lecithin:Cholesterol Acyltransferase)
Formation of cholesterol esters in lipoproteins

18. • CHYLOMICRON AND VLDL
• Chylomicrons and VLDL are synthesised in intestinal mucosal
cells and liver cells respectively.
• Polysomes on rough endoplasmic reticulum of these tissues
synthesis apo-B48 and apo-B100.
LIPOPROTEIN METABOLISM

21. VLDL

22. LDL
• LDL ( Low Density Lipoproteins )
– Transports cholesterol from liver to the tissues
– Synthesized in the liver
– Approximately 50 % by weight cholesterol
– Most atherogenic lipoprotein … “ Bad Cholesterol “

23. LDL

25. HDL
• Good cholesterol.
• Account for 20-30% of cholesterol in blood.
• Transport excess of cholesterol from the tissues back to the
liver (reverse transport).
• Synthesized in liver and intestine.

27. CETP (Cholesteryl ester transfer protein)
• CETP is an enzyme protein , synthesised in the liver. If
facilitates the transfer of cholesteryl esters from HDL to VLDL
or LDL, in exchange of TG.

28. CLINICAL ASPECT
• In Japan, a group of people have a genetic mutation that
causes high levels of HDL, and have a low incidence of heart
disaease.
• People lack the enzyme protein CETP due to genetic
mutation , which increase HDL.
• Pfizer Inc has developed an oral drug, Torcetrapib which
blocks CETP producing increased level of HDL.

29. LIPOPROTEIN (a) [LP(a)]
• It is a special type of lipoprotein not present in all people.
• In normal individuals it may be present only in 20% of the
population.
• In 20% of normal individuals , if present , it is found to be
more than 30 mg/dl. When present , it is attached to apo-
B100 by a disulphide bond.

30. CLINICAL IMPORTANCE
• Indians have a higher level of LP (a) than in the western
population.
• The persons having LP(a) are more susceptible to heart attack
at the younger age of 30 to40 years.
• LP (a) inhibits fibrinolysis. Levels more than 30mg/dl increases
the risk of myocardial infarction by 3 times .

31. CLINICAL DISORDERS
• HYPERLIPOPRPTEINAEMIAS
 Familial Lipoprotein Lipase Deficiency:
• A rare disorder and is characterised by Hypertriglyceridaemia
(TG) and Hyperchylomicronaemia.
• Enzyme deficiency: lipoprotein lipase.
• Feature: (1)Eruptive Xanthomas.
(2) recurrent abdominal pain

32. ATHEROSCLEROSIS
• Atherosclerosis is a slowly progressive disease of muscular
arteries and large arteries characterised by evevated
deposition of cholesterol in form of plaque.
• Plaque formation:
(1) Increased Plasma cholesterol.
(2) Increased plasma LDL.
(3) Decreased plasma HDL.

34. PREVANTION AND TREATMENT
(1) Exercise.
(2) Weight control.
(3) Alcohol consumption
(4) Stopping of smoking.
(5) Diet.
(6) Niacin therapy.

35. RECENT ADVANCES: ARTIFICAL HDL
• A tiny particles in the laboratory by nanotechnology that
mimic the natural HDL good Cholesterol, and they scooping
up the cholesterol before it can grow up into dangerous
deposit of plaque.
• The surface of these numoparticles are coated with fats are
protein as they can bind tightly with the sticky cholesterol to
transport it though block stream to liver for degradation.

36. IMPORTANCE
• Serve to transport lipids and lipid-soluble compounds
between tissues and organs
– Substrates for energy metabolism (TG)
– Essential components for cells (PL, C)
– Precursors for hormones (C)
– Lipid soluble vitamins
– Precursors for bile acids (C)

37. CONCLUSION
• Molecular complexes that consist of lipids and proteins. They function
as transport vehicles for lipids in blood plasma.
• Lipoproteins deliver the lipid components (cholesterol and
triglyceride etc.) to various tissues for utilization.

38. REFERENCE
• MN Chatterjea , Rana shinda -Medical
Biochemistery.
• INTERNET.