Biosynthesis of membrane lipids and steroids 1

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Biosynthesis of membrane lipids and steroids 1

• Léránt István

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BIOSYNTHESIS OF MEMBRANE LIPIDS
Fatty acid 1
Fatty acid 1
Glycerol
Fatty acid 2
Glycerol
Fatty acid 2

• Phosphatydic acid is a
• COMMON INTERMEDIER of biosynthesis of
• phospholipids
• Neutral fats

Fatty acid 3
P
Alcohol
Glycerol-phosphate acyltransferase
Neutral fats
Phospholipids
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In most tissues Glycerol / glycerol-kinase
LIver
Adipose tissue Glycolysis - DHAP
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SYNTHESIS of MEMBRANE LIPIDS and TRIGLYCERIDS

• Phosphatydic acid is a
• COMMON INTERMEDIER of biosynthesis of
• phospholipids
• Neutral fats
• ACYL-GLYCEROL-SYNTHETASE COMPLEX
• ENDOPLASMIC RETICULUM
• Phosphatase
• Diacylglycerol acyltransferase

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SYNTHESIS OF MEMBRANE LIPIDS

• BIOSYNTHESIS OF PHOSPHOLIPIDS
• ACTIVATION OF PHOSPHATIDIC ACID / ALCOHOL

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SYNTHESIS OF PHOSPHATIDYLINOSITOL 4,5 BISPHOSPHATE

• CDP-diacylglycerol
• Phosphatidyl-inositol
• Phosphatidyl-inositol
• 4,5 bisphosphate

Phospholipase C
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Cardiolipin - component of the mitochodrial
membranes
Phosphatidyl - glycerol
Diophosphatidyl glycerol Cardiolipin
pH / 7,0 pK H3PO4 / 1 - 2
Mitochondria / Lues
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Cardiolipin - component of the mitochodrial
membranes
CTP
P-
P-
CDP
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PHOSPHATIDYL-CHOLINE

• CHOLINE
• Food sources
• Circulation
• Presynaptic cholinergic membrane
• Choline-transport - high affinity Synthesis of
  phosphatidyl-choline in hepatocytes from
  phosphatidyl-ethanolamine

Cytoplasm Endoplasmic reticulum
CTPphosphocholine cytidyliltranspherase
Choline-kinase
CDP-CHOLINE 1,2-diglyceride Phosphocholine
ltranspherase
Endoplasmic reticulum
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PHOSPHATIDYLETHANOLAMINEPHOSPHATIDYL-C
HOLINELIVER
CHOLINE
CHOLINE-P
CDP-CHOLINE
PHOSPHATIDYL- CHOLINE
CO2
3 S-adenosyl- homocysteine
3 SAM
PHOSPHATIDYL SERINE
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PHOSPHATIDYLETHANOLAMINEPHOSPHATIDYL-C
HOLINELIVER
CHOLINE
CHOLINE-P

• RATE LIMITING STEP
• CTPphosphocholine cytidylil-transferase
• Cytoplasm Endoplasmic reticulum
• Translocation - activation
• fatty acid fatty -acyl-CoA / DAG
• cAMP dependent protein kinase
• Lipid transport PCh dependent
• Choline deficiency / VLDL / fatty liver

CDP-CHOLINE
PHOSPHATIDYL- CHOLINE
CO2
3 S-adenosyl- homocysteine
3 SAM
PHOSPHATIDYL SERINE
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Sphingolipids
Sphingosine
Sphingosine
Fatty ecid
Fatty acid
Ceramide


Glu / Gal
P
Choline
Sphingosine (4-sphingenene)
X
P
Sphingomyeline
Choline
Glu
Glucosyl-cerebroside
Sphingosine
Glu
Gal
Fatty acid
Lactosyl-cerebrozide

NeuNAc
X
GM2 ganglioside
Glu
Gal
GalNAc
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Sphingomyelin
Fatty acid
Phosphoric acid
Sphingosine
Ceramide
Choline
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Synthesis of sphigolipids
Galactocerebrosides Glucocerebrosides Gangliosides
sphyngomyeline
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Glucosyl-ceramide / Glucocerebroside
Ceramide
Glu
Monohexoside
Glu
Gal
Dihexoside
Ceramide
Ceramide
Glu
Gal
Gal
Trihexoside
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Galactosyl ceramide / Galactocerebroside
Ceramid
Gal
Monohexoside
Gal
Gal
Dihexozid
Ceramid
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ABO blood group system
Glu
Gal
GalNAc
Gal
O (H) antigen
Fuc
Glu
Gal
GalNAc
Gal
GalNAc
A antigen
Fuc
Glu
Gal
GalNAc
Gal
Gal
B antigen
Fuc
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Gangliosides
Glu
Ceramide
Gal
GM3
NANA
Ceramide
Glu
Gal
GalNAc
GM2
NANA
Ceramide
Glu
Gal
GalNAc
GM1
Cholera toxin
Gal
NANA
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Inborn errors of phospholipid, sphingolipid
metabolism

• Demyelination Sclerosis multiplex
• White matter decrease of phospholipid,
  plasmenyl ethanolamine, sphingolipid
• Sphingolipidosis
• Accumulation of complex lipids
• Synthesis of complex lipids is not effected
• Lack of specific (hydrolytic) lysomal enzymes
• All tissues are effected
• Multiple sulfatase deficiency

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Sphingolipidoses
sphingomyelinase
Ceramid
P-Kol
Niemann-Pick

• Accumulation of sphingomyelin

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Gauchers - disease

• Accumulation of glucocerebrosides in
  reticuloendothelial cells of spleen, liver, and
  bone marrow
• the most common of lysosomal storage disease
• Mental retardation

Glu
b-glukozidáz
Ceramid
Gaucher
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Krabbe disease

• Accumulation of Galactosyl ceramide

Gal
b-galaktosidase
Ceramid
Krabbe
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Tay Sachs Disease

• Deficiency of Hexosaminidase A
• Hexosaminidase A
• hydrolyses the N-acetyl-galactosamine of GM2
  ganglioside
• Mental retardation
• Macrocephalia
• Death at age 2-4
• Frequency Ashkenazi Jewish population 13500

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Tay Sachs Disease
Glu
Gal
GalNAc
Ceramid
Tay - Sachs
NANA
hexosaminidase
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Sphingolipidoses
Glu
Gal
Gal
Ceramide
Fabry
a-galactosidase
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CHOLESTEROL

• Cholesterol is the most highly decorated small
  molecule in biology. Thirteen Nobel Prizes have
  been awarded to scientists who devoted major
  parts of their careers to cholesterol. Ever since
  it was isolated from gallstones in 1784,
  cholesterol has exerted an almost hypnotic
  fascination for scientists from the most diverse
  areas of science and medicine. Cholesterol is a
  Janus-faced molecule. The very property that
  makes it useful in cell membranes, namely its
  absolute insolubility in water, also makes it
  lethal.
• Michael Brown and Joseph Goldstein
• Nobel Lectures (1985)

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CHOLESTEROL

• Cholesterol is the most highly decorated small
  molecule in biology. Thirteen Nobel Prizes have
  been awarded to scientists who devoted major
  parts of their careers to cholesterol. Ever since
  it was isolated from gallstones in 1784,
  cholesterol has exerted an almost hypnotic
  fascination for scientists from the most diverse
  areas of science and medicine. Cholesterol is a
  Janus-faced molecule. The very property that
  makes it useful in cell membranes, namely its
  absolute insolubility in water, also makes it
  lethal.
• Michael Brown and Joseph Goldstein
• Nobel Lectures (1985)

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CHOLESTEROL

• Cholesterol is the most highly decorated small
  molecule in biology. Thirteen Nobel Prizes have
  been awarded to scientists who devoted major
  parts of their careers to cholesterol. Ever since
  it was isolated from gallstones in 1784,
  cholesterol has exerted an almost hypnotic
  fascination for scientists from the most diverse
  areas of science and medicine. Cholesterol is a
  Janus-faced molecule. The very property that
  makes it useful in cell membranes, namely its
  absolute insolubility in water, also makes it
  lethal.
• Michael Brown and Joseph Goldstein
• Nobel Lectures (1985)

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CHOLESTEROL

• SYNTHESIS OF
• Active isoprenoid-units isopentenyl-pirophosphat
  e
• Acetyl-CoA à 3-hydroxy-3-methyl-glutaryl-CoA
  (HMG-CoA)
• HMG-CoA à mevalonate
• Mevalonate à isopentenyl-PP
• 6 isopentenyl-pyrophosphate à squalen
• Cyclisation of squalen à cholesterol

• Acetyl CoA C27
• Synthesis cytosolic compartment
• Endoplasmic reticulum bound enzymes
• All cells
• LIVER
• Adrenal cortex
• Testis
• Ovaries
• Intestinal epithelia

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Steps of cholesterol biosynthesis I
Koleszterin-bioszintézis
Ketontest-képzés
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Steps of cholesterol biosynthesis II

• Rate limiting step in cholesterol biosynthesis

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Steps of cholesterol biosynthesis III

• Mevalonic acid ATP à
• 5-pyrophospho-mevalonate
• 5-pyrophospho-mevalonate à decarboxylation
  active isoprenoid unit

Prenylated proteins, ubiquinon, heme,
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Steps of cholesterol biosynthesis IV
5
5

• Dimethylallyl-PP isopentenyl-PP Geranyl-PP (5
  5) 10
• Geranyl PP isopentenyl-PP farnesyl-PP (10
  5) 15
• Farnesyl-PP Farnesyl-PP Squalene (15 15 )
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• NADPH H
• PPi
• Squalene -syntase Endoplasmic reticulum

10
5
15
15
30
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Steps of cholesterol biosynthesis V

• Cyclization
• Monooxygenase
• C2,3 epoxide
• Transfer of Methylgroups
• 14-13, 8 14
• Sterol carrier protein 1 (SCP1)
• Squalene
• Sterol carrier protein 2 (SCP2)
• Lanosterol

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Steps of cholesterol biosynthesis V

• 1 molecule of cholesterol
• 18 acetyl-CoA
• 36 ATP
• 16 NADPH

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Regulation of cholesterol biosynthesis

• Regulation of HMG-CoA biosynthesis
• HMG-CoA reductase mRNS synthesis (transcription)
• HMG-CoA reductase mRNS translation
• HMG-CoA reductase degradation
• covalent modification - phosphorylation

• Cholesterol - food
• de novo synthesis
• Liver
• Intestine
• Rate of biosynthesis is influenced by
• Intracellular cholesterin synthesis
• Comitted step HMG-CoA reductase

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REGULATION OF CHOLESTEROL BIOSYNTHESIS
Cholesterolá
Cholesterol â

• Regulation of biosynthesis of HMG-CoA
• HMG-CoA reductase mRNS synthesis (transcription)
• HMG-CoA reductase mRNS translation
• HMG-CoA reductase degradation
• covalent modification - phosphorylation
• Sterol regulatory element binding protein
  (SREBP)
• SREBP cleavage activating protein (SCAP)

HMG-CoA reductase
INSIG-1
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REGULATION OF CHOLESTEROL BIOSYNTHESIS

• Regulation of biosynthesis of HMG-CoA
• HMG-CoA reductase mRNS synthesis (transcription)
• HMG-CoA reductase mRNS translation
• HMG-CoA reductase degradation
• covalent modification - phosphorylation
• Sterol regulatory element binding protein
  (SREBP)
• SREBP cleavage activating protein (SCAP)

X formed from mevalonate
cholesterol of food origin
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REGULATION OF CHOLESTEROL BIOSYNTHESIS

• Regulation of biosynthesis of HMG-CoA
• HMG-CoA reductase mRNS synthesis (transcription)
• HMG-CoA reductase mRNS translation
• HMG-CoA reductase degradation
• covalent modification - phosphorylation
• Sterol regulatory element binding protein
  (SREBP)
• SREBP cleavage activating protein (SCAP)
• HMG-CoA reductase
• Cytoplasmatic domain katalysis
• Membrane domain sensor cholesterol cc
• Enzyme proteolytic cleavage, ubiquitine,
  proteasome

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REGULATION OF CHOLESTEROL BIOSYNTHESIS

• Regulation of biosynthesis of HMG-CoA
• HMG-CoA reductase mRNS synthesis (transcription)
• HMG-CoA reductase mRNS translation
• HMG-CoA reductase degradation
• covalent modification - phosphorylation
• Sterol regulatory element binding protein
  (SREBP)
• SREBP cleavage activating protein (SCAP)

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LIPIDTRANSPORT
Hepatocyta - VLDL
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Chylomicrons
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VLDL
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HDL
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LDL
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Bile acids
Tauro Gliko
Tauro Glyco
Cholesterol
Chenodeoxycholic acid
Litocholic acid
Cholic acid
Primary bile acid
Deoxycholic acid
Secondary bile acids
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Biosynthesis of bile acids
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Enterohepatic circulation
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Bile bile acids, phosphatidyl-choline,
cholesterol
phosphatidylcholine
cholesterol
5, 15, 80
Bile acid