MPS 587 - Advanced Plant Biochemistry Course

Lipids section guest lecture:Philip Bates

Post-doc Browse labOffice: 453 Clark Hall

Email: phil_bates@wsu.edu

Lecture 9Lipids I

1. What is a lipid?2. Fatty acids3. Lipid classes: structures and functions4. Lipid analysis

Today’s topic on the node map

What is a lipid?

Historical definitionLipids are HYDROPHOBIC or AMPHIPATHIC molecules that are typically soluble in organic

solvents

Lipids are fatty acids (FA) and their derivatives, and substances related biosynthetically or functionally to these compounds.

William W. Christie, Scottish Crop Research Institute(http://www.lipidlibrary.co.uk/index.html)

Fatty acids are carboxylic acids containing a aliphatic chain of an even (typically) number of carbons.

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Very little FA accumulate as free fatty acids, most fatty acids are found esterified as oxygen or sulfur (thio) esters or as amide bonds

Palmitoyl-CoA

Phosphatidylcholine

Protein myristoylation

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Functions of lipids

Membranes and compartmentalization Energy storage

Caloric content per gram:Fat = 9Protein = 4Carbohydrates = 4

Protection against pathogens and water loss

Substrates for signaling and defense compounds

(Pollard et al. (2008) Trends in Plant Science 13: 236)

(Browse J (2005) In Vitamins & Hormones, Vol. 72, Academic Press, p 431)

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Fatty acids and derived metabolites

Saturated normal-chain fatty acidsSystematic

nameTrivial name

Shorthand

Designation

ethanoic acetic 2:0

propanoic propionic 3:0

butanoic butyric 4:0

pentanoic 5:0

hexanoic caproic 6:0

heptanoic 7:0

octanoic caprylic 8:0

nonanoic 9:0

decanoic capric 10:0

undecanoic 11:0

dodecanoic lauric 12:0

tridecanoic 13:0

tetradecanoic myristic 14:0

pentadecanoic 15:0

hexadecanoic palmitic 16:0

heptadecanoic margaric 17:0

octadecanoic stearic 18:0

nonadecanoic 19:0

eicosanoic arachidic 20:0

heneicosanoic 21:0

docosanoic behenic 22:0

tricosanoic 23:0

tetracosanoic lignoceric 24:0

pentacosanoic 25:0

hexacosanoic 26:0

heptacosanoic 27:0

octacosanoic 28:0

nonacosanoic 29:0

triacontanoic 30:0

hentriacontanoic 31:0

dotriacontanoic 32:0

(http://www.lipidlibrary.co.uk/Lipids/fa_sat/index.htm)

NomenclatureNumber of carbons : number of double bonds

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Monoenoic normal-chain fatty acids

Systematic name Trivial nameShorthanddesignation

cis-9-tetradecenoic myristoleic 9-14:1 or 14:1(n-5)

cis-7-hexadecenoic 7-16:1 or 16:1(n-9)

cis-9-hexadecenoic palmitoleic 9-16:1 or 16:1(n-7)

cis-6-octadecenoic petroselinic 6-18:1 or 18:1(n-12)

cis-9-octadecenoic oleic 9-18:1 or 18:1(n-9)

cis-11-octadecenoic cis-vaccenic 11-18:1 or 18:1(n-7)

cis-11-eicosenoic gondoic 11-20:1 or 20:1(n-9)

cis-13-docosenoic erucic 13-22:1 or 22:1(n-9)

cis-15-tetracosenoic nervonic 15-24:1 or 24:1(n-9)

trans-3-hexadecenoic 3t-16:1

trans-9-octadecenoic elaidic 9t-18:1

trans-11-octadecenoic vaccenic 11t-18:1

(http://www.lipidlibrary.co.uk/Lipids/fa_mono/index.htm)

Eladic acid, 9t-18:1

Steric acid, 18:0

Nomenclature of double bondsΔ = count from carboxyln = ω = count from methyl end

Oleic acid, 18:1(n-9)

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Polyunsaturated fatty acids

methylene-interrupted

n-6

n-3

conjugated

polymethylene-interrupted

(http://www.lipidlibrary.co.uk/Lipids/fa_conj+/index.htm)

Substituted fatty acidshydroxylated epoxy

furanoid methoxylated(algae)

(http://www.lipidlibrary.co.uk/Lipids/eicplant/index.htm)

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ω-6 and ω-3 Fatty acids are essential in the human diet

Linoleic acid (18:2 Δ9, 12)

α-Linolenic acid (18:3 Δ9, 12, 15)

Wallis JG, Watts JL, Browse J (2002) Polyunsaturated fatty acid synthesis: what will they think of next? Trends in Biochemical Sciences 27: 467-473

EPAMany nutritionally important fatty acids are produced in algae

Essential fatty acids

Eicosapentaenoic acid (EPA) 20:5n3

Docosahexaenoic acid (DHA) 22:6n3

Supplemented with algal DHA

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Lipid Classes1. Simple or Neutral lipids

Triacylglycerols (TAG)

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

• Primary components of fats and oils.

• Consist of glycerol moiety with each hydroxyl group esterified to a fatty acid.

• Primary function: energy storage.

Diacylglycerols (DAG)

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

• Key intermediates in the biosynthesis of triacylglycerols and other lipids.

• Cellular messengers (generated by hydrolysis of phosphatidylinositol and related metabolites by phospholipase C).

• Intermediate of the enzymatic hydrolysis of triacylglycerols

2-Monoacyl-sn-glycerols (MAG)

• Formed as intermediates or end-products of the enzymatic hydrolysis of triacylglycerols.

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm10

http://www.scientificpsychic.com/fitness/fattyacids1.html

Effect of cis double bonds on lipid properties

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15

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25

30

35

40

16:0 18:0 18:1 18:2(n-6) 18:3(n-3)

mo

l %

Cocoa butter

0

10

20

30

40

50

60

70

80

16:0 18:0 18:1 18:2(n-6) 18:3(n-3)

mo

l %

Olive oil

Physical state of purified plant oils (TAG)

Solid

Liquid

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Sterols and sterol esters

http://www.lipidlibrary.co.uk/Lipids/plant_st/index.htm

• More information in lectures about isoprenoids.

Tocopherols

• More information in lectures about isoprenoids.

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

Epicuticular Waxes (not discussed here)

Cutins (not discussed here)

Stigmasterol

Surface lipids

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2. Complex or polar lipids (membrane lipids)Glycerolphospholipids

Phosphatidylglycerol (PG)

Phosphatidylcholine (PC)

Phosphatidylethanolamine (PE)

Phosphatidylserine (PS)

Phosphatidylinositol (PI)

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

Polar glycerolipid general structure

• Glycerol backbone• sn-1 and sn-1 FA• sn-3 polar headgroup

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Phosphatidic acid (PA)

Cardiolipins (CL)

• Exclusively in mitochondria.

http://www.lipidlibrary.co.uk/lipids/dpg/index.htm

Lyso-lipids

• Intermediate in glycerolipid synthesis• Signaling molecule generated by lipase digestion of phospholipids

Lyso-phosphatidic acid (LPA)

Lyso-phosphatidycholine acid (LPC)

• Intermediate in glycerolipid synthesis

• Intermediate in acyl editing

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Galactolipids

Sulfolipid

http://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

• Primarily in plant plastids.

• Exclusively in plant plastids.

MGDG DGDGhttp://www.lipidlibrary.co.uk/Lipids/whatlip/index.htm

SQDG

Non-phosphorous containing glycerolipids

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Glucosylceramides / Sphingolipids

(Sperling & Heinz (2003) Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 1632: 1)

• non-glycerol based membrane lipids• Also involved in signaling and stress responses

Basic ceramide structure and modifications

Long chain bases (LCB)

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3. Membrane lipid structure/function

(Lingwood & Simons (2010) Science 327: 46)

Lipid Rafts As a Membrane-Organizing Principle.

(Melser et al. (2011) Plant Cell Reports 30: 177)

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Liquid crystalline phase due to fatty acid unsaturation

Fatty acid desaturase mutants are more susceptible to cold

Membrane dynamics allows compartmentalization and trafficking

(Miquel et al. (1993) Proceedings of the National Academy of Sciences of the USA 90: 6208)

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Li-Beisson et. al. (2010) In The Arabidopsis Book 8:e0133. doi:10.1199/tab.0133Figure 8

Lipid abundance

Li-Beisson et. al. (2010) In The Arabidopsis Book 8:e0133. doi:10.1199/tab.0133Figure 21.

Li-Beisson et. al. (2010) In The Arabidopsis Book 8:e0133. doi:10.1199/tab.0133Figure 22.

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Lipid class composition in different tissues

Headgroup Maize (leaves)

Wheat (roots)

Soybean (seeds)

PhospholipidsPC 6 50 1-3

PE 3 35 1-3

PG 7 4 1-3

PI 1 6 1-3

CL 1 0 1-3

GalactolipidsMGDG 42 1-5 0.4-1.0

DGDG

SQDG

31

5

1-5

1-5

0.4-1.0

0.4-1.0

TAG 0.2-1.0 1-5 90-95

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Lipid class composition in different organelles

Headgroup Chloroplast (thylakoid)

Mitochondrion (inner membrane)

Plasmamembrane

PhospholipidsPC 3 27 32

PE 0 29 46

PG 9 0 0

PI 1 0 19

PS

CL

0

0

25

20

0

0

GalactolipidsMGDG 51 0 0

DGDG

SQDG

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7

1-2

0

0

0

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Li-Beisson et. al. (2010) In The Arabidopsis Book 8:e0133. doi:10.1199/tab.0133. Table 4.

Fatty acid content/composition of Arabidopsis tissues

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Lipid analysis

1. Lipid extraction• Separate lipids from aqueous soluble

material with organic solvents2. Separate/determine lipid classes

• Thin-Layer Chromatography (TLC)• HPLC• Mass spectrometry* (LC-MS/MS)

• Lipidomics3. Determination of fatty acid content

• Convert lipid classes to fatty acid methyl esters (FAME) and quantify by GC-FID

• Mass spectrometry* (LC-MS3)• Lipidomics

General analysis outline

Li-Beisson Y et. al. (2010) Acyl-Lipid Metabolism. The Arabidopsis Book 8:e0133. doi:10.1199/tab.0133http://www.bioone.org/doi/full/10.1199/tab.0133

Analysis references

Christie WW (2003) Lipid Analysis: Isolation, Separation, Identification and Structural Analysis of Lipids, Ed 3rd. The Oily Press an imprint of PJ Barnes & Associates, Bridgwater, England

http://lipidlibrary.aocs.org/

http://www.k-state.edu/lipid/lipidomics/

Kansas Lipidomics Research Center

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Lipid analysis

Neutral lipids

MGDG

PG

DGDG

SQDG

PSPI

PE

PC

TLC separation of polar lipids

Arabidopsis: Leaf Seed

GC-FID of individual lipid classes

Make FAME

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16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 20:2 22:1

mo

l %

Developing Arabidopsis seed FA compositions

PC

PE

TAG

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Lipid analysis

(Welti et al. (2002) Journal of Biological Chemistry 277: 31994)

Lipid molecular speciesNumber of total FA carbons : number of total double bonds

Mass spectrometry analysis of lipids

http://www.k-state.edu/lipid/lipidomics/profiling.htm

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