Why discuss the topic of: lipid Biosynthesis? Lipids as

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 energy

source 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 system and used as liquid fuels

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

alcoholysis /al·co·hol·y·sis/ (al″kah-hol´ĭ-sis) decomposition of a compound 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 OXYLIPINS

Plants Animals

LIPASE

COXs LOXs CYP450

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 Biosynthesis

A: 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 have a chain length of 16 or 18 carbons, and contain

one to three cis double bonds.

Five major fatty acids:

™16:0

™16:3, make up over 90% of the acyl-chains of the structural glycerolipids of all plant membranes

™18:1

™18:2

™18:3

** 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-ACP

18:1 R-CoA

PLASTID 4:0-ACP

Acetyl-CoA ACP 12:0-ACP 14:0-ACP 18:0-ACP 16:0-ACP

P

P-Choline P R R

MEMBRANE LIPIDS

OILBODY

CYTOPLASM CPT

R

R R R R

R P R

R ACP

18:0 16:0

Malonyl-CoA CO

CO

2

2

TAG

DAGAT GPAT

LPAAT

PAP

ACCase

KASIII THIOESTERASE

∆9-DESATURASE

6:0-ACP 8:0-ACP 10:0-ACP

KASI KASII

Lipid Biosynthesis

18:1-ACP

18:1 R-CoA

PLASTID 4:0-ACP

Acetyl-CoA ACP 12:0-ACP 14:0-ACP 18:0-ACP 16:0-ACP

P

P-Choline P R R

MEMBRANE LIPIDS

OILBODY

CYTOPLASM CPT

R

R R R R

R P R

R ACP

18:0 16:0

Malonyl-CoA CO

CO

2

2

TAG

DAGAT GPAT

LPAAT

PAP

ACCase

KASIII THIOESTERASE

∆9-DESATURASE

6:0-ACP 8:0-ACP 10:0-ACP

KASI KASII

Membrane

Essential Constituent, of all cells:

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

ƒ Delineate the cell & its compartment

ƒ Site 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 nonpolar

hydrocarbon 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-ACP

18:1 R-CoA

PLASTID 4:0-ACP

Acetyl-CoA ACP 12:0-ACP 14:0-ACP 18:0-ACP 16:0-ACP

P

P-Choline P R R

MEMBRANE LIPIDS

OILBODY

CYTOPLASM CPT

R

R R R R

R P R

R ACP

18:0 16:0

Malonyl-CoA CO

CO

2

2

TAG

DAGAT GPAT

LPAAT

PAP

ACCase

KASIII THIOESTERASE

∆9-DESATURASE

6:0-ACP 8:0-ACP 10:0-ACP

KASI KASII

Sn-1 Plants: mono and polyunsaturated 18carbons

B- Plant oil as an alternative source of biofuel:

Sn-2 Sn-3 Animals: Saturated TAGS

Plant TAGs:

• Plant storage lipids are important components of human and animal diets.

• Industrial use: detergents, paints, lubricants. Loosely defined as 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 Oils

acetyl-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]

Soybean Cotton Canola Safflower Sunflower Maize

Flax Sesame

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 OXYLIPINS

Plants Animals

LIPASE

COXs LOXs CYP450

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 OXYLIPINS

Plants Animals

LIPASE

COXs LOXs CYP450

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 1.6

P = <0.001

∗

M oc k

AA

Lesion diameter (cm)

Mock AA

AA enhanced resistance to Botrytis is mediated via JA pathway

1000

JA (ng/g FW)

800

600

400

200

Mock AA

Mock AA

Biotic and abiotic stress signals PLD

AOC AOS LOX2

OPR3 JA

VSP2

JA , ng/g fw

0 1 2 3

4 ∗

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

AA induces JA levels in tomato

Lesion area (cm2 ) P = 0.004

0 0.2 0.4 0.6 0.8

1

∗

Mock AA

Mock AA

0 1 2 3 4

AA

JA (ng/g f.w.)

Mock

RSRE response to

Botrytis infection

Multimerized RSREs are sufficient to confer rapid responses to both

biotic and abiotic stresses in vivo

RSRE = ATAACGCGTTTTTA

4X RSRE LUCIFERASE

THUS

RSRE is a functional motif involved

in primary stress responses

Rapid Stress Response Element (RSRE)

RSRE = ATAACGCGTTTTTA

4X RSRE LUCIFERASE

Time (min)

Bioluminescence

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 Leaf Background

Walley et al., PLoS Gent 07

AA elicits expression of

4XRSRE:LUC

AA elicits expression of 4XRSRE:LUC

350

Bioluminescence

AA

Mock

100 150 200

50 100 150 200 250 300

Time (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 disease

Science 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 Acids

acetyl-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

chloroplast/proplastid C8:0 C10:0

Free fatty acids

acyl-CoAs

Structural lipids

Storage lipids

{further desaturation}

endoplasmic reticilum

MCTs and their application

Comprised primarily of caprylic (8:0) and capric (10:0) Application:

A: Food

ƒFull and Pre-term infant formula

ƒAthletic supplements

B: Nutrition/Pharmaceutical

ƒOral, enteral and IV nutrition:

Digested, and absorbed and transported rapidly

ƒDietetic/low calorie food:

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

ƒKetogenic, a diet traditionally given to drug resistance children with epilepsy to improve seizure control

ƒControlling diarrhea and fat malabsorption in HIV-positive patients

ƒPotentially, as part of ketogenic diet in slowing tumor growth

C: Industrial

Biogradable lubricants and Biodiesel