Lipids transport

6/9/2014 7:39:25 AM 1uploaded by elhadi hassan

By
Dr. Elrasheed Eltaher Osman

 Dietary lipids and de novo synthesized lipid
by adipose tissue and liver must be
transported between various tissues and
organs for utilization and storage.
 Lipids are insoluble in water
 The problem arises of how to transport
this non-polar molecules in aqueous
environment (the blood)

The problem solved through
transporters called lipoproteins
They are amphipathic molecules
(two phases polar and non-polar)

 Definition
 Classes
 Components
 The apolipoproteins
 Description of each class
 Metabolism

These are complex lipids containing
protein that transport lipid in the
blood
They are amphipathic molecule

Classify according to density into
1- chylomicron
2- very low density lipoprotein
(VLDL)
3- low density lipoprotein (LDL)
4- high density lipoprotein (HDL)

Classify according to movement
in eletrophoresis into
1- preβ-lipoprotein
2- β-lipoprotein
3- α-lipoprotein

Consist of
1- lipids
2- proteins

 This consist of
1- phospholipids
2- cholesterol
3- triacylglycerol
4- cholesteroylester
 The 2 above make outer membrane
 The 2 below found inside making the
core

Called apolipoproteins
They are either integral part or
freely exchangeable proteins
Nomenclature :using the letters A,
B, C, D, and E
Sub classes represent by latin
number I, II, III and IV example
apo A I, II, III, and IV apo C I, II and
III
Apo B are two B100 and B48 (only
48% of the length of the first)

Structural function apoB
Receptor ligand apo E
Enzyme activator apo A-I
Enzyme inhibitor apo A-II
Transporter apo D (lipid transfer
protein)

 Include
1- Apo B100
2- Apo B48
3- Apo A- I.II.III and IV
4- Apo C- I.II and III
5- Apo E
6- Apo D

 Is the of longest polypeptide (4536 aa)
 Is glycoprotein
 Synthesize in the liver
 Found in VLDL, IDL and LDL
 Integral protein play structural role as
well as receptor ligand for LDL receptor

 Is about 48 % of the length of Apo B100
Contain 2153 amino acids
Synthesized by intestine
Play structural role in chylomicron

Four types I, II, III and IV
Found in HDL exchange with other
LPs (chylomicrons)
Apo A-I is activator of enzyme LCAT
and ligand for HDL receptor
Apo A-II is two identical polypeptides
joint by disulfide bridge inhibitor of
Apo A-I and LCAT
Apo A-IV associated with formation of
triacylglycerol –riched LP
(chylomicron)

 Three types Apo C-I, II and III
 Small polypeptides freely transferable
between the different LPs
 Apo C-I found in VLDL, HDL and
chylomicron and is possiblr activator of
LCAT
Apo C-II found in VLDL, HDL and
chylomicron and is activator of
lipoprotein lipase
Apo C-III found in VLDL, HDL and
chylomicron and is polymophous (due
to sialic acid content) inhibitor of Apo
C-II

 Found in VLDL, IDL, LDL, chylomircon
and chylomicron reminants
 Integral protein
 Is a ligand for chylomicron reminant
receptor in liver and LDL receptor in
extra-hepatic tissue

 Is the large in size lest in density LPs
 Synthesized by intestine
 Carried the dietary lipid (triacylglycerol
and cholesterol)
 About 88% is triacylglycerol
 Contains Apo B48, Apo A (I,II) and Apo C

Found in certain HDL subfraction
May act as transporter
Called lipid transfer protein

Chylomicrom
Very low density lipoprotein (VLDL)
Low density lipoprotein (LDL)
High density lipoprotein (HDL)

Lymph Enterocyte
Intestinal
Lumen
With
apoB48 Cholesteryl
Ester
Triglyceride
Phospholipid

 Secret in lymph goes to extrahepatic tissue
(mainly adipose tissue)first where are
metabolized
 Metabolized by lipoprotein lipase to free
fastty acid and chylomiron reminants
 The chylomicron reminant goes to the liver
where further metabolism occur
 The chylomicron reminant entr the liver
through receptor mediated pinocytosis

Enzyme hydrolyzed tracylglycerol
ninto fatty acids and glycerol
Found in blood vessels near extra-
hepatic tissue mainly adipose tissue,
heart and muscle
It is partculate enzyme anchored to
endothelium by( –ve proteoplycan
chain of heparan sulfate),bond
that is released by administration
of heparin

 Synthesized and secreted by liver
 Carries lipid synthesized inside the liver
 Carried about 60 % triacylglycerol
 Contain Apo B100, Apo C and Apo E
 Metabolyzed by lipoprotein lipase into
intermediate density lipoprotein IDL and
LDL

Synthesized in the blood from other
LPs mainly VLDL
Carried cholesterol to extra-hepatic
tissue
Responsible for high blood
cholesterol (bad cholesterol)
Contain Apo B100 and Apo E
Most of LDL degraded in liver
through Apo B100 and E receptors
A positive correlation exist between
incidence of coronary
atherosclerosis and plasma
concentration of LDL

 Is synthesized and secreted from both liver
and intestine
 Contains Apo A, C and E
 Nascent HDL from intestine lack Apo C and E
gain them when enter the blood from hepatic
HDL
 HDL act as repository for Apo C and E that
required for metabolism of VLDL and
chylomicrons

 The nascent HDL consists of discoid PL bi-
layers containing Apo A and free cholesterol
 When joins the enzyme LCAT
(lecithin,cholesterol :acyltransferase) the free
cholesterol esterified by one fatty of the PLs
to form cholesteroylester and
lysophospholipid
 Cholesteroylester in non-polar moves to
hydrophobic interior of the bi-layer where
lysolecithin is transferred to plasma albumin

 LCAT continues forming CE that migrates
to interior forming non-polar core the
HDL become spherical in shape
 LCAT system remove the unesterified
cholesterol from lipoprotein and from
tissue
 HDL cycle account for transporting
cholesterol from tissue to liver (good
cholesterol) n process called reverse
cholesterol transport

Lipids transport

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Lipids transport

Similar to Lipids transport (20)

Recently uploaded

Recently uploaded (20)

Lipids transport