mps 587 - advanced plant biochemistry course lipids...
Post on 26-Apr-2018
227 Views
Preview:
TRANSCRIPT
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.
3
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
4
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)
5
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
6
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)
7
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)
8
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
9
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
0
5
10
15
20
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
11
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
12
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
13
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
14
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
15
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)
16
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)
17
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)
18
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.
19
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
20
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
26
7
1-2
0
0
0
21
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
22
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
23
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
0
5
10
15
20
25
30
35
40
45
50
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
24
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
25
top related