Biosynthesis of membrane lipids and steroids 1

Biosynthesis of membrane lipids and steroids 1

Léránt István

BIOSYNTHESIS OF MEMBRANE LIPIDSPhosphatydic acid is a COMMON INTERMEDIER of biosynthesis of

phospholipidsNeutral fats

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Glycero

l

Fatty acid 1

Fatty acid 2

Fatty acid 3

Glycero

l

Fatty acid 1

Fatty acid 2

P Alcohol

Neutral fats Phospholipids

Glycerol-phosphate acyltransferase

In most tissuesGlycerol / glycerol-kinase

LIver

Adipose tissue:Glycolysis - DHAP

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SYNTHESIS of MEMBRANE LIPIDS and TRIGLYCERIDSPhosphatydic acid is a COMMON INTERMEDIER of biosynthesis of

phospholipidsNeutral fats

ACYL-GLYCEROL-SYNTHETASE COMPLEXENDOPLASMIC RETICULUM

PhosphataseDiacylglycerol acyltransferase

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SYNTHESIS OF MEMBRANE LIPIDSBIOSYNTHESIS OF PHOSPHOLIPIDSACTIVATION OF PHOSPHATIDIC ACID / ALCOHOL

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SYNTHESIS OF PHOSPHATIDYLINOSITOL 4,5 BISPHOSPHATECDP-diacylglycerolPhosphatidyl-inositolPhosphatidyl-inositol4,5 bisphosphate

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Phospholipase C

Cardiolipin - component of the mitochodrial membranes

CH2

C

CH2

O

O

HO

P

O

O

O

CR2

C R1

O

OCH2

C OHH

CH2 O P

O

O

O CH2

C O C

O

R3

CH2OC

O

R4

H

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Phosphatidyl - glycerolPhosphatidyl - glycerol

Diophosphatidyl – glycerol; CardiolipinDiophosphatidyl – glycerol; Cardiolipin

PP-- PP--

pH ~ / = 7,0 pK’ HpH ~ / = 7,0 pK’ H33POPO44 ~ / = 1 - 2 ~ / = 1 - 2

Mitochondria / LuesMitochondria / Lues

Cardiolipin - component of the mitochodrial membranes

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ncardiolipiylglycerolphosphatid

ylglycerolphosphatid(PGP) P-ylglycerolphosphatid

(PGP) P-ylglycerolphosphatideroldiacylglycCDP

eroldiacylglycCDPatephosphatid

atephosphatid P-3-Glycerol

eroldiacylglyc-CDP

ylationdephosphor

synthase PGP

synthaseDAG -CDP

heraseacyltransp phosphate-3-glycerol 2

PP-- PP--CTPCDP

PHOSPHATIDYL-CHOLINECHOLINE:

Food sourcesCirculationPresynaptic cholinergic membraneCholine-transport - high affinity Synthesis of phosphatidyl-choline in hepatocytes from phosphatidyl-ethanolamine

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Choline-kinaseCTP:phosphocholine cytidyliltranspherase

CytoplasmEndoplasmic reticulumEndoplasmic reticulum

Endoplasmic reticulumEndoplasmic reticulum

CDP-CHOLINE: 1,2-diglyceride Phosphocholine ltranspherase

PHOSPHATIDYLETHANOLAMINE&PHOSPHATIDYL-CHOLINELIVER

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CHOLINE

CHOLINE-P

CDP-CHOLINE

PHOSPHATIDYL-CHOLINE

PHOSPHATIDYLSERINE

CO2 3 SAM3 S-adenosyl-homocysteine

PHOSPHATIDYLETHANOLAMINE&PHOSPHATIDYL-CHOLINELIVERRATE LIMITING STEP:CTP:phosphocholine cytidylil-transferase

Cytoplasm – Endoplasmic reticulumTranslocation - activation

+ fatty acid – fatty -acyl-CoA / DAG

cAMP dependent protein kinase

Lipid transport – PCh dependentCholine deficiency / VLDL / fatty liver

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CHOLINE

CHOLINE-P

CDP-CHOLINE

PHOSPHATIDYL-CHOLINE

PHOSPHATIDYLSERINE

CO2 3 SAM3 S-adenosyl-homocysteine

Sphingolipids

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P Choline

X

Sphingomyeline

Glu Glucosyl-cerebroside

Glu GalGal Lactosyl-cerebrozide

GluGlu GalGal GalNAcGalNAc

NeuNAc

GM2 ganglioside

Sphingosine

Fatty ecid

P Choline

Sphingosine

Fatty acid

Glu / Gal

Ceramide

Sphingosine

Fatty acid

X

CH C3

C2

CH2

1

H

OH

H

NH3

+OHCH

szfingozin (4-szfingenin)Sphingosine (4-sphingenene)

Sphingomyelin

CH C3

C2

CH2

1

H

OH

H

NH2

+

O

CH C R

O

P O

O

O

CH2 CH2 N+

CH3

CH3

CH3

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Sphingosine Ceramide Choline Phosphoric acid

Fatty acid

Synthesis of sphigolipids

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sphyngomyeline

GalactocerebrosidesGlucocerebrosides

Gangliosides

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Glucosyl-ceramide / Glucocerebroside

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CeramideCeramideGluGluMonohexosideMonohexoside

CeramideCeramide

GluGluGalGalDihexosideDihexoside CeramideCeramide

GluGluGalGalGalGalTrihexosideTrihexoside

Galactosyl – ceramide / Galactocerebroside

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CeramidCeramidGalGalMonohexosideMonohexoside

GalGalGalGalDihexozidDihexozid CeramidCeramid

ABO blood group system

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Glu GalGal GalNAc Gal

Fuc

Glu GalGal GalNAc Gal

Fuc

Glu GalGal GalNAc Gal

Fuc

Gal

GalNAc

„O” (H) antigen

„A” antigen

„B” antigen

Gangliosides

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CeramideCeramideGluGluGalGal

NANANANA

GGM3M3

CeramideCeramideGluGluGalGal

NANANANA

GalNAcGalNAcGGM2M2

CeramideCeramideGluGluGalGal

NANANANA

GalNAcGalNAcGGM1M1

GalGal

Cholera toxinCholera toxin

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

• Accumulation of sphingomyelin

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CeramidCeramid P-KolP-KolNiemann-PickNiemann-Pick sphingomyelinase

Gaucher’s - disease

• Accumulation of glucocerebrosides in reticuloendothelial cells of spleen, liver, and bone marrow

• the most common of lysosomal storage disease• Mental retardation

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CeramidCeramid GluGluGaucherGaucher -glukozidáz-glukozidáz

Krabbe disease

• Accumulation of Galactosyl ceramide

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CeramidCeramid GalGalKrabbeKrabbe -galaktosidase

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 1:3500

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Tay – Sachs DiseaseTay – Sachs Disease

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CeramidCeramid GluGlu

hexosaminidase

GalGal

NANA

GalNAcGalNAcTay - SachsTay - Sachs

Sphingolipidoses

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CeramideCeramideFabryFabry GluGlu GalGal GalGal

-galactosidase-galactosidase

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 GoldsteinNobel 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 GoldsteinNobel 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 GoldsteinNobel Lectures (1985)

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CHOLESTEROL

• SYNTHESIS OF • Active isoprenoid-units –

isopentenyl-pirophosphate • Acetyl-CoA 3-hydroxy-3-methyl-

glutaryl-CoA (HMG-CoA)– HMG-CoA mevalonate– Mevalonate isopentenyl-PP

• 6 isopentenyl-pyrophosphate squalen

• Cyclisation of squalen cholesterol

Acetyl CoA – C27

Synthesis – cytosolic compartmentEndoplasmic reticulum bound enzymes

All cellsLIVERAdrenal cortexTestisOvariesIntestinal epithelia

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Steps of cholesterol biosynthesis I

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mevalonateCoAglutarylmethyl3hydroxy3

CoAglutarylmethyl3hydroxy3CoA-acetyl CoA lacetoacety

CoAlacetoacetyCoA-acetyl 2

reduktase-CoA-HMG

syntaseCoA HMG

thiolase

Koleszterin-bioszintézis

Ketontest-képzés

-OOC

CH3 OH

CoA

O

-OOC

CH3 OH OH

3-Hidroxi-3metil-glutaril-CoA mevalonát

2 NADPH+H+ 2 NADP+

CoASH

HMG-CoA reduktáz

Steps of cholesterol biosynthesis IIRate limiting step in cholesterol biosynthesis

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Steps of cholesterol biosynthesis IIIMevalonic acid + ATP 5-pyrophospho-mevalonate

5-pyrophospho-mevalonate decarboxylation + active isoprenoid unit

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Prenylated proteins, ubiquinon, heme,

Steps of cholesterol biosynthesis IVDimethylallyl-PP + isopentenyl-PP = Geranyl-PP (5 + 5) = 10

Geranyl –PP + isopentenyl-PP = farnesyl-PP (10 + 5) = 15

Farnesyl-PP + Farnesyl-PP = Squalene (15 + 15 )= 30

NADPH + H+ -PPi

Squalene -syntase – Endoplasmic reticulum

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5

5

10

15

5

30

15

Steps of cholesterol biosynthesis VCyclizationMonooxygenaseC2,3 epoxide

Transfer of Methylgroups14-13, 8 – 14

Sterol carrier protein 1 (SCP1)Squalene

Sterol carrier protein 2 (SCP2)Lanosterol

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Steps of cholesterol biosynthesis V1 molecule of cholesterol

18 acetyl-CoA36 ATP16 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 - foodde novo synthesis

LiverIntestine

Rate of biosynthesis is influenced byIntracellular cholesterin synthesis

Comitted step: HMG-CoA reductase

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REGULATION OF CHOLESTEROL BIOSYNTHESISRegulation of biosynthesis of HMG-CoA

HMG-CoA reductase mRNS synthesis (transcription) HMG-CoA reductase mRNS translationHMG-CoA reductase degradationcovalent modification - phosphorylation

Sterol regulatory element binding protein (SREBP)

SREBP cleavage activating protein (SCAP)

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HMG-CoA reductase

CholesterolCholesterolCholesterol

INSIG-1

REGULATION OF CHOLESTEROL BIOSYNTHESISRegulation of biosynthesis of HMG-CoA

HMG-CoA reductase mRNS synthesis (transcription)HMG-CoA reductase mRNS translationHMG-CoA reductase degradationcovalent modification - phosphorylation

Sterol regulatory element binding protein (SREBP)

SREBP cleavage activating protein (SCAP)

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X formed from mevalonateX formed from mevalonate

cholesterol of food origin cholesterol of food origin

REGULATION OF CHOLESTEROL BIOSYNTHESISRegulation of biosynthesis of HMG-CoA

HMG-CoA reductase mRNS synthesis (transcription)HMG-CoA reductase mRNS translationHMG-CoA reductase degradationcovalent modification - phosphorylation

Sterol regulatory element binding protein (SREBP)

SREBP cleavage activating protein (SCAP)

HMG-CoA reductaseCytoplasmatic domain – katalysisMembrane domain – sensor cholesterol ccEnzyme proteolytic cleavage, ubiquitine, proteasome

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REGULATION OF CHOLESTEROL BIOSYNTHESISRegulation of biosynthesis of HMG-CoA

HMG-CoA reductase mRNS synthesis (transcription)HMG-CoA reductase mRNS translationHMG-CoA reductase degradationcovalent modification - phosphorylation

Sterol regulatory element binding protein (SREBP)

SREBP cleavage activating protein (SCAP)

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LIPIDTRANSPORT

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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

OH

OH OHH

OH

COOH

OH OHH

COOH

OHH

OH

COOH

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OHH

COOHCholesterolCholesterol

Primary bile acidPrimary bile acid

Secondary bile acidsSecondary bile acids

Cholic acid

Chenodeoxycholic acidChenodeoxycholic acid

Deoxycholic acid

Litocholic acid

Tauro ~Glyco ~

Tauro ~Gliko ~

NH

CH2 CH2 SO3H

NH

CH2 COOH

Biosynthesis of bile acids

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Enterohepatic circulation

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Bile: bile acids, phosphatidyl-choline, cholesterol

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cholesterol %phosphatidylcholine %

Bile acid %

5, 15, 80 %