Why discuss the topic of:lipid Biosynthesis?

Lipids as:

- Biofuels

Dehesh UC Davis

Fossil fuel is believed to be derived from ancient lipid rich organic material such as spores and planktonic algae!

Rudolf Diesel used peanut oil as liquid fuels in internal combustion engines (1900)

Because of its low cost and easy availability, petroleum became the dominant energysource and petroleum diesel was then developed as the primary fuel for diesel engines

Petroleum and its derivatives fuels were in short supply in 1930 and hence in the 1930s and 1940s, neat vegetable oils were used in diesel engines under an emergency situation (Ma and M.A. Hanna, 1999. Biodiesel production: a review, Bioresource Technology 70 :1–15. ) During this period two approaches were used:

1- Hydrocarbons were produced in China by a Tung oil pyrolysis batch systemand used as liquid fuels

2- Fatty acids’ ethyl or methyl esters, obtained by transesterification oralcoholysis of vegetable oils

alcoholysis /al·co·hol·y·sis/ (al″kah-hol´ĭ-sis) decomposition of acompound due to the incorporation and splitting of alcohol

Why discuss the topic of:lipid Biosynthesis?

Lipids as:

- Biofuels- protective agents

C- Cuticular lipids are protective agents

• Found in surface of all terrestrial plants.Crucial hydrophobic barrier to prevent H2O loss & protection

against pathogens & other environmental stresses. Contain:1- Cutin: polymer of 16 + 18 carbon hydroxyl fatty acids cross linked by esterification of their carboxyl groups to hydroxyl groups of neighboring acyl-chain.2- Wax esters: a mixture of long-chain fatty acids, and fatty alcohols and esters.

Why discuss the topic of:lipid Biosynthesis?

Lipids as:

- Biofuels- protective agents

- Signaling compounds

Fatty acids as signaling molecules

OXYLIPINSPlants Animals

LIPASE

COXs CYP450LOXs

arachidonic acid

LIPASE

arachidonic acid

CYP450

LIPASE

arachidonic acid

LOXs CYP450

LIPASE

arachidonic acid

COXs LOXs CYP450

LIPASE

arachidonic acid 20:4

Why discuss the topic of:lipid Biosynthesis?

Lipids as:

- Biofuels- protective agents

- Signaling compounds- Pharmaceutical

Fatty Acids and Health

Lorenzo’s oil ( a blend of trierucin/triolein)A cure to adrenoleukodystrophy (ADL), an X-linked disorder

Lipid Biosynthesis

Classes of Lipids

A. Major Class:The most abundant type are derived from fatty acid and glycerolipid biosynthetic pathway.

B. Minor Class:Derived from isoprenoid pathway and there are over 25000 isoprenoid compounds. Mostly are "Secondary metabolites" not found in all cells (not essential to growth).

Sterols, gibberellins, abscisic acid + phytol side chain of chlorophyll are from this pathway.

The Fatty Acid biosynthesis is a Primary Metabolic Pathway:in all cells, essential for growth. No mutation or inhibitors : lethal.

Lipid BiosynthesisA: membrane B: Carbon Storage

C- Cuticular lipids

In plants plastids are the predominant site of FA biosynthesis

Fatty acids in animals and fungi are produce in the cytosol

Major fatty acids in plants

Fatty acids in plants, and most other organisms havea chain length of 16 or 18 carbons, and contain

one to three cis double bonds.Five major fatty acids:

16:016:3, make up over 90% of the acyl-chains of the

structural glycerolipids of all plant membranes18:118:218:3

** Never as Free Fatty acids in cells, instead, their carboxyl group is esterified or otherwise modified.They are esterified to glycerols “ glycerolipids”

Lipid Biosynthesis

18:1-ACP18:1 R-CoA

PLASTID

4:0-ACP

Acetyl-CoA ACP

12:0-ACP

14:0-ACP

18:0-ACP

16:0-ACP

P

P-CholineR RPMEMBRANE

LIPIDS

OILBODY

CYTOPLASM

CPT

R

RR

RR

PRR

R

ACP18:016:0

Malonyl-CoA

CO

CO

2

2

TAG

DAGAT

GPAT

LPAAT

PAP

ACCaseKASIII

THIOESTERASE

∆9-DESATURASE

6:0-ACP

8:0-ACP

10:0-ACPKASI

KASII

Lipid Biosynthesis

18:1-ACP18:1 R-CoA

PLASTID

4:0-ACP

Acetyl-CoA ACP

12:0-ACP

14:0-ACP

18:0-ACP

16:0-ACP

P

P-CholineR RPMEMBRANE

LIPIDS

OILBODY

CYTOPLASM

CPT

R

RR

RR

PRR

R

ACP18:016:0

Malonyl-CoA

CO

CO

2

2

TAG

DAGAT

GPAT

LPAAT

PAP

ACCaseKASIII

THIOESTERASE

∆9-DESATURASE

6:0-ACP

8:0-ACP

10:0-ACPKASI

KASII

MembraneEssential Constituent, of all cells:Vegetative cells of plant contain 5-10% lipid by dry weight, mostly found in membranes

Delineate the cell & its compartmentSite of essential processes such as light harvesting &

electron transport of photosynthesis

Membrane glycerolipids have fatty acids attached to both the Sn-1 and Sn-2 position of glycerol backbone. Polar headgroup attached to Sn-3 position.

Fatty Acids

Combination of polar and nonpolar -> amphipathic property of glycerolipids -> an essential property for the formation of membrane bilayer.

Membrane

glycerophospholipid has: 1- A polar region: glycerol, carbonyl oxygens of fatty acids, phosphate, and the polar head group .

2- Two nonpolarhydrocarbon tails of fatty

acids.

Structures of the major fatty acids and glycerolipids of plant cell membrane

Mutants plants with altered FA composition

Membrane composition and cold tolerance

Distribution of lipid classes

B: Carbon Storage:

Plant use reduced carbon derived from photosynthesis to store energy. Main forms of reserves are Carbohydrates, protein & oils. Oils most efficient form of energy storage carbons in Fatty acids are highly reduced (more than carbohydrates), and therefore oxidation of oils release twice as much energy as the oxidation of carbohydrates or proteins. Many seeds synthesize oil in developing seeds to act as energy source in germination. In some species up to 60% of seed dry weight is oil.

Lipid Biosynthesis

18:1-ACP18:1 R-CoA

PLASTID

4:0-ACP

Acetyl-CoA ACP

12:0-ACP

14:0-ACP

18:0-ACP

16:0-ACP

P

P-CholineR RPMEMBRANE

LIPIDS

OILBODY

CYTOPLASM

CPT

R

RR

RR

PRR

R

ACP18:016:0

Malonyl-CoA

CO

CO

2

2

TAG

DAGAT

GPAT

LPAAT

PAP

ACCaseKASIII

THIOESTERASE

∆9-DESATURASE

6:0-ACP

8:0-ACP

10:0-ACPKASI

KASII

Sn-1 Plants: mono and polyunsaturated 18carbons

B- Plant oil as an alternative source of biofuel:

Sn-2Sn-3 Animals: Saturated TAGS

Plant TAGs:

• Plant storage lipids are important components of human andanimal diets.

• Industrial use: detergents, paints, lubricants. Loosely definedas H2O insoluble compounds- extractable by organic

solvent such as chloroform.

Three positions of glycerol esterified with Fatty acid ->triacylglycerol (TAG) -> major form of lipids in TAG:

Fatty Acids in Common Vegetable Oilsacetyl-CoA

C4:0-ACP

C6:0-ACP

C8:00-ACP

C10:0-ACP

C12:0-ACP

C14:0-ACP

C16:0-ACP

C18:0-ACP

C18:1-ACP

C16:0

C18:0

C18:0 [C18:2, C18:3]

SoybeanCottonCanolaSafflowerSunflowerMaizeFlaxSesame

Diversity in structure and hence application of lipids

C- Cuticular lipids are protective agents

• Found in surface of all terrestrial plants.Crucial hydrophobic barrier to prevent H2O loss & protection

against pathogens & other environmental stresses. Contain:1- Cutin: polymer of 16 + 18 carbon hydroxyl fatty acids cross linked by esterification of their carboxyl groups to hydroxyl groups of neighboring acyl-chain.2- Wax esters: a mixture of long-chain fatty acids, and fatty alcohols and esters.

Fatty acids as signaling molecules

OXYLIPINSPlants Animals

LIPASE

COXs CYP450LOXs

arachidonic acid

LIPASE

arachidonic acid

CYP450

LIPASE

arachidonic acid

LOXs CYP450

LIPASE

arachidonic acid

COXs LOXs CYP450

LIPASE

arachidonic acid 20:4

Fatty acids as signaling molecules

Minor amount of fatty acid are precursors to hormone &Jasmonic acid (a component of signal transduction pathway)

Fatty acids as signaling molecules

Jasmonic acid (a component of signal transduction pathway)JA is a plant growth regulator derived form 18:3, and is capable of induction of plant defense genes, at low concentrations.

Biosynthesis and structure of jasmonate is very similar to that of eicosanoids that are central to inflammatory responses in mammals.

JA protects plants from insects

Fatty acids as signaling molecules

OXYLIPINSPlants Animals

LIPASE

COXs CYP450LOXs

arachidonic acid

LIPASE

arachidonic acid

CYP450

LIPASE

arachidonic acid

LOXs CYP450

LIPASE

arachidonic acid

COXs LOXs CYP450

LIPASE

arachidonic acid 20:4

AA treatment enhances resistance to Botrytis

0

0.4

0.8

1.2

1.6P = <0.001

∗

Mock AA

Lesi

on d

iam

eter

(cm

)

Mock AA

AA enhanced resistance to Botrytis is mediated via JA pathway

1000

JA (n

g/g

FW) 800

600

400

200

Mock AA 0

Mock AA

Biotic and abiotic stress signals

PLD

AOC

AOS

LOX2

OPR3

JA

VSP2

JA, n

g/g

fw

0

1

2

3

4 ∗

Mock 18:2 18:3 20:2 20:3 AA

AA induces JA levels in tomato

Lesi

on a

rea

(cm

2 )

P = 0.004

0

0.2

0.4

0.6

0.8

1 ∗

MockAA

Mock AA

0

1

2

3

4

AA

JA (n

g/g

f.w.)

Mock

RSRE response to Botrytis infection

Multimerized RSREs are sufficient to confer rapid responses to bothbiotic and abiotic stresses in vivo

RSRE = ATAACGCGTTTTTA4X RSRE LUCIFERASE

THUSRSRE is a functional motif involved

in primary stress responses

Rapid Stress Response Element (RSRE)

RSRE = ATAACGCGTTTTTA

4X RSRE LUCIFERASE

Time (min)

Bio

lum

inesc

en

ce

400

600

800

1000

1200

1400

1600

-45 5 55 105 155 205 255 305

W

4xRSRE Wounded Leaf

4xRSRE Systemic Leaf

Vector Control Wounded LeafBackground

Walley et al., PLoS Gent 07

AA elicits expression of4XRSRE:LUC

AA elicits expression of4XRSRE:LUC

350

Bio

lum

inesc

en

ce

AAMock

100

150

200

50 100 150 200 250 300Time (min)

500

Fatty acids and disease

Lorenzo’s oil ( a blend of trierucin/triolein)A cure to adrenoleukodystrophy (ADL), an X-linked disorder

Fatty acids and diseaseScience 1998 Jun 5;280(5369):1607-10

Inhibition of a Mycobacterium tuberculosis beta-ketoacyl ACP synthase by Isoniazid

Fatty-acid synthase and human cancer:new perspectives on its role in tumor biology

Nutrition 2000 Mar;16(3):202-8

Science 2000 Apr 7;288(5463):140-3

Specialized fatty acid synthesis in African trypanosomes: myristate for GPI anchors.

Medium Chain Fatty Acidsacetyl-CoA

C4:0-ACP

C6:0-ACP

C8:00-ACP

C10:0-ACP

C12:0-ACP

C14:0-ACP

C16:0-ACP

C18:0-ACP

C18:1-ACPchloroplast/proplastid

C8:0C10:0

Free fatty acids

acyl-CoAs

Structurallipids

Storagelipids

{further desaturation}

endoplasmic reticilum

MCTs and their applicationComprised primarily of caprylic (8:0) and capric (10:0)Application:A: FoodFull and Pre-term infant formulaAthletic supplementsB: Nutrition/PharmaceuticalOral, enteral and IV nutrition:

Digested, and absorbed and transported rapidlyDietetic/low calorie food:

Oxidized rapidly in the organism and hence low tendency todeposit as body fat

Ketogenic, a diet traditionally given to drug resistance children with epilepsy to improve seizure controlControlling diarrhea and fat malabsorption in HIV-positive patientsPotentially, as part of ketogenic diet in slowing tumor growthC: IndustrialBiogradable lubricants and Biodiesel