Transcript CH 2 - Faperta UGM

Agricultural Product
Starch
Lipid
Organic waste
Carbohydrate producing
plant
• Corn
• Rice
• Sago
• Tuber crop
Annual lipid producing plant
1.
Peanut
Arachis hypogea
2.
3.
Winged bean
Soybean
Psophocorpus tetragonolobus
Glycine max
4.
Corn
Zea mays
5.
Rice
Oryza sativa
6.
Sesame
Sesamum indicum
7.
Sunflower
Helianthus annuus
Perrenial lipid producing plant
1.
Castor
Ricinus communis
2.
Jatropa
Jatropa curcas
3.
Kapok
Ceiba petandra
4.
Rubber
Hevea brasiliensis
5.
Coconut
Cocos nucifera
6.
Moringa
Moringa oleifera
7.
Nutsege
Aleurites mollucana
8.
Kusambi
Sleichera trijuga
9.
Oil palm
Elais guineensis
10.
Avocado
Persea gratissima
11.
Cacao
Theobroma cacao
12.
Kepoh
Sterculia foetida
13.
Nyamplung
Callophylum inophylum
14.
Randu
Bombax malabaricum
15.
Tengkawang
Shorea stenoptera
Carbohydrate
A group of organic compounds that includes sugars and related
compounds
Sugar
1. Compounds with between 3 – 7 carbon atoms having many
hydroxyl (alcohol) groups and either a ketone group or an
aldehyde group
2. A convenient source of energy
3. Raw material for many chemical syntheses
4. Water soluble
Sugar
Triose
Glyceraldehyde
Dihydroxyacetone
Tetroses
Erythrose
Threose
Arabinose
Ribose
Xylose
Glucose
Fructose
Galactose
Mannose
Pentose
Hexose
Disaccharides
Two molecules of a simple sugar linked together
Sucrose
Lactose
Cellobiose
Maltose
Polysaccharides
Long chain of simple sugar
Two main functions:
1. Storage
2. Structure
Storage carbohydrate
 A way of storing nutrients for future needs
 To cover periods when its ability to supply nutrients from
photosynthesis is inadequate (during growth and regeneration)
 The commonest are starches and starch like materials
 It is stored at seeds or tuber
Starch
A mixture of two different types of molecules:
1. amylose (a long chain of glucose joint by α-1,4 linkages)
2. amylopectin (a mixture of α-1,4 links with occasionally α-1,6 branches
In general, amylopection accounts for about 70% of starch
Starch from different source vary in ratio of amylose and
amylopectin
Plants use glyoxylate cycle to convert
lipids to carbohydrates
Plants use glyoxylate cycle to convert
lipids to carbohydrates
Starch biosynthesis is growing from
reducing end
o
Glc P P
Starch
synthase
Xa
Xb
o
Glc
o
Glc
o
o
Glc
o
Glc
o
Glc
o
Glc
Glc P P
o
Glc
o
Glc
o
Glc
Sucrose biosynthesis
• Sucrose is synthesized in cytosol by sucrose
6-phosphate synthase and sucrose 6phosphate phosphatase.
Sucrose 6-phosphate synthase is also regulated
G 6-P
Pi
P
Sucrose 6phosphate
synthase
SPS
kinase
SPS
PPase
Sucrose 6-phosphate
synthase is regulate by
phosphorylation/dephospho
rylation.
Starch biosynthesis is regulated by
ADP-glucose pyrophosphorylase
Lipid
 Any of a group of organic compounds consisting of the
fats and other substances of similar properties,
insoluble in water but soluble in fats solvent and alcohol
 Structurally diverse range of compounds which have 2
features in common: (1). Their presence in living
organism and (2). Their general solubility in organic
solvent and insolubility in water
 It is characterized by the presence of fatty acid moieties
and which are best described as acyl lipids
Plant lipid
 Most plants do not store large quantities of lipids, with the
exception of some oilseeds
 Most lipid in plants have structural role as component of
membranes and are synthesized in each cells
 Plant do not transport fatty and complex lipids between their
tissue
 The most important plant tissues involved in lipid biosynthesis
are the seeds
 Seeds produce large quantities of triacylglicerols
 Large agricultural and food industry has developed around the
extraction and utilization of lipids from oil seeds
Acyl Lipid
Neutral
More readily soluble in non polar hydrocarbon solvents such as light
petroleum and benzene
Glycerides (triacylglycerols): trihydroxy alcohol glycerols
Waxes (fatty acid esters of long chain monohydroxy alcohols)
Polar
Much more soluble in polar solvents like ethanol
Phospholipids (diester of orthophosphoric acids)
Glycolipids (one or more monosaccharide residues)
Acyl Lipid Structure
 Major fatty acids
All saturated and unsaturated monocarboxylic acids with an unbranched, even
numbered carbon chain
Palmitic, oleic and linoleic acids often predominate
In general, saturated acids are less abundant than unsaturated acid
 Minor fatty acids
Two main categories: (1). Saturated and the cis-mono unsaturated acids,
(2)polyunsaturated acids
 Unusual fatty acids
Fatty acids which have (1) non-conjugated double bonds which are trans or in an
unusual position, (2). Conjugated double bond systems, (3). Allenic double
bonds, (4). triple bonds, (5). Oxygen functions and (6). Branched chain
The Major Plant Fatty Acids
Common name
Symbol
Structure
Lauric acid
12:0
CH3-(CH2)10-COOH
Myristic acid
14:0
CH3-(CH2)12-COOH
Palmitic acid
16:0
CH3-(CH2)14-COOH
Stearic acid
18:0
CH3-(CH2)16-COOH
Oleic acid
18:1 (9c)
CH3-(CH2)7-CH=CH-(CH2)7-COOH
Linoleic acid
18:2(9c,1 CH3-(CH2)4-(CH2-CH=CH)22c)
(CH2)6-COOH
α-linoleic acid
18:3(9c,1 CH3-(CH2)-(CH2-CH=CH)3-(CH2)72c,15c)
COOH
Glycerides
 Fatty acid esters of trihydroxy alcohol
 The fast majorities in nature have all 3 of glycerol hydroxy groups
esterified with fatty acids and are called triglycerides
(triacylglycerols)
 They are the main constituents of natural fats and oil
 Food reserves in seeds and/or fleshy part of fruit
 Serve as carbon store in seeds required for biosynthesis
processes during seed germination not as an energy store
 Triacylglycerols have an advantage over carbohydrate as
storage compounds due to their weight/carbon content ratio is
much lower
Glycerides
 Carbon in the seed as fat requires less than half the weight as
when stored as starch
 Low weight is advantageous for seed dispersal
 They are deposited in oil bodies which consist of oil droplet
which are surrounded by a lipid monolayer
 Synthesis of glycerides occur in ER membrane
 Apart from their obvious value to the plants, they are of
enormous commercial importance
Phospholipid
 Glycerophospholipids
 Sphingophospholipids
Glycolipid
 Galactosyldiglycerides
 Cerebrosides
 sulpholipids
LIPID BIOSYNTHESIS
• Fatty acid biosynthesis-basic fundamentals
• Fatty acid biosynthesis-elongation and
desaturation
• Triacylglycerols
Fatty Acid Biosynthesis
Synthesis
 Cytosol
 Requires NADPH
 Acyl carrier protein
 D-isomer
 CO2 activation
 Keto  saturated
Beta Oxidation
 Mitochondria
 NADH, FADH2
 CoA
 L-isomer
 No CO2
 Saturated  keto
Rule
Fatty acid biosynthesis is a stepwise assembly
of acetyl-CoA units (mostly as malonyl-CoA)
ending with palmitate (C16 saturated)
3 Phases
Activation
Elongation
Termination
ACTIVATION
CH3C~SCoA
O
HCO3-
ATP
ADP + Pi
-OOC-CH
2C~SCoA
O
active carbon
Acetyl-CoA carboxylase
1. Acetate is the basic two-carbon unit
from which fatty acids are synthesis
2. It must be first converted to acetylCoA
3. Acetyl-CoA is produced in large
quantities from pyruvate in
mitochondria of photosynthetic tissue
or from glucose via the glycolitic
pathway in non-photosynthetic tissue
4. In addition to acetyl CoA, malonyl
CoA is an essential substrate for
fatty acid synthesis and is produced
by the carboxylation of acetyl CoA,
catalyzed by Acetyl-CoA carboxylase
Acetyl-CoA Carboxylase
The rate-controlling enzyme of FA synthesis
• In Eukaryotes - 1 protein
(1) Single protein, 2 identical polypeptide
chains
(2) Each chain Mwt = 230,000 (230 kDa)
(3) Dimer inactive
(4) Activated by citrate which forms
filamentous form of protein that can be seen in
the electron microscope
Acetyl-CoA Carboxylasein Plants
1. It is located in the chloroplasts in leaf tissue and in plastids in seeds
2. Unlike the enzyme in animal tissue, this is not activated by citrate,
instead small changes in stromal pH or Mg or K concentration can
markedly affect enzyme activity
3. The enzyme is also regulated by a heat stable factor found in leaves
and is influenced by the ratio of ADP to ATP
4. High ATP levels activate the enzyme
Initiation
Overall Reaction
Malonyl-CoA + ACP
-OOC-CH
CH3C~SCoA
2C~S-
O
O
CO2
HS-CoA
CH3C-CH2C~SO
ACP
+ HS-CoA
Acyl Carrier
Protein
ACP
O
NOTE
Malonyl-CoA carbons become new COOH end
Synthesis of long chain saturated
fatty acids from acetyl-CoA and
malonyl-CoA
1. It take place on a complex enzyme called fatty acid synthetase
2. FA synthetase 3 groups:
a. Type I synthetase found in animals, yeast and some bacteria
b. Type II synthetases occur in most bacteria and plant tissue
c. Type III synthetase involved in the elongation of existing fatty acid
-Carbon
Elongation
CH3C-CH2C~S-
NADPH
D isomer
O
Reduction
O
-Ketoacyl-ACP reductase
H
CH3C-CH2C~SHO
O
-H2O
NADPH
ACP
ACP
Dehydration
 -Hydroxyacyl-ACP dehydrase
H
CH3C-= C- C~S- ACP
H
O
Enoyl-ACP reductase
CH3CH2CH2C~S- ACP
O
Reduction
TERMINATION
-KS
Transfer to Malonyl-CoA
Ketoacyl ACP
Synthase
Transfer to KS
-S-ACP
-CH2CH2CH2C~S- ACP
Free to bind
Malonyl-CoA
O
Split out CO2
CO2
When C16 stage is reached, instead of transferring to KS,
the transfer is to H2O and the fatty acid is released
Fatty Acid Synthase
O
S-C-CH2-CH2-CH3
-Ketoacyl
-ACP synthase
KS
O
CH3-CH2-CH2-C-S
Acetyl-CoA
HS
CoA-SH
NADP+
Enoyl-ACP
reductase NADPH
H+
O
CH3-CH=CH-C-S
-Hydroxyacyl-ACP H2O
KS
ACP
Initiation or
priming
O
S-C-CH3
SH
Malonyl-CoA
Malonyl-CoACoA-SH ACP transacylase
O
O
S -C-CH2-COO-
CH3-CH -CH2-C-S
-Ketoacyl
-ACP reductase
O
S -C-CH3
KS -SH
dehydrase
OH
Acetyl-CoAACP transacylase
KS
NADP+
NADPH
H+
S
C=O
CH2
C=O
CH3
-Keto-ACP
synthase (condensing enzyme)
CO2
KS -SH
Elongation
Substrate Entry
Reduction
Thioesterase
palmitate release
AT
MT
DH KR
ER ACP
CE
CH2
Translocation
HS
HS
TE
SH
SH
Translocation
CH2
CE
TE
Thioesterase
palmitate release
ACP ER KR DH
Reduction
MT
AT
Substrate Entry
Overall Reactions
Acetyl-CoA + 7 malonyl-CoA + 14NADPH + 14H
7H++
Palmitate + 7CO2 + 14NADP+ + 8 HSCoA + 6H2O
7 Acetyl-CoA + 7CO2 + 7ATP
7 malonyl-CoA +7ADP + 7Pi + 7H+
8 Acetyl-CoA + 14NADPH + 7H+ + 7ATP
Palmitate + 14NADP+ + 8 HSCoA + 6H2O + 7ADP + 7Pi
PROBLEM:
Fatty acid biosynthesis takes place in the
cytosol. Acetyl-CoA is mainly in the
Mitochondria
acetyl-CoA
How is acetyl-CoA made available to the cytosolic
fatty acyl synthase?
SOLUTION:
Acetyl-CoA is delivered to cytosol from the
mitochondria as CITRATE
CH2COO
HO-C-COO
mitochondria
CH2COO
CH2COO
HO-C-COO
OAA
CO2
Pyr
Acetyl-CoA
Citrate lyase
COO
C=O
OAA
Malate
CH2
dehydrogenase
COO
NADH
CH2COO
Acetyl-CoA
HS-CoA
L-malate
CO2
COO
HO-C-H L-malate
CH2
COO Malic enzyme
NADP+
NADPH + H+
COO
C=O Pyruvate
CH3
Cytosol
Post-Synthesis Modifications
 C16 satd fatty acid (Palmitate) is the product
Elongation
Unsaturation
Incorporation into triacylglycerols
Incorporation into acylglycerol phosphates
Elongation of Chain (two systems)
R-CH2CH2CH2C~SCoA Malonyl-CoA*
O
(cytosol)
HS-CoA
OOC-CH2C~SCoA CH3C~SCoA
CO2
O
O
Acetyl-CoA
(mitochondria)
R-CH2CH2CH2CCH2C~SCoA
O
O
1 NADPH
Elongation systems are
NADH
found in smooth ER and
2 - H2O
3 NADPH
mitochondria
R-CH2CH2CH2CH2CH2C~SCoA
O
Rules:
Desaturation
The fatty acid desaturation system is
in the smooth membranes of the endoplasmic
reticulum
There are 4 fatty acyl desaturase enzymes in
mammals designated 9 , 6, 5, and 4 fatty
acyl-CoA desaturase
Mammals cannot incorporate a double bond
beyond 9; plants can.
Mammals can synthesize long chain unsaturated
fatty acids using desaturation and elongation
Rule: The Desaturase System requires O2 and
resembles an electron transport system
NADH
2
Cyt b5
reductase
O2
Cyt b5
3
(FAD)
Saturated FA-CoA
1
2
NOTE:
1. System is in ER membrane
2. Both NADH and the fatty acid contribute electrons
3. Fatty acyl desaturase is considered a mixed function
oxidase
Fatty acid desaturation system
C18-stearoly-CoA
C18 9-oleyl-CoA
+ O2 + 2H+
+ 2H2O
Desaturase
Desaturase
2 cyt b5 Fe2+
2 cyt b5 Fe2+
Cyt
b5
2H+ + cyt b5 reductase
FAD
NADH + H+
cyt b5 reductase
FADH2
NAD+
Cyt b5
reductase
Desaturase
Palmitoleate
16:1(9)
Palmitate
16:0
Elongase
Stearate
18:0
Permitted
transitions
in mammals
Desaturase
Essential
fatty acid
Desaturase
-Linolenate
18:3(9,12,15)
Other lipids
Oleate
18:1(9)
Desaturase
Linoleate
18:2(9,12)
Desaturase
-Linolenate
18:3(6,9,12)
Elongase
Eicosatrienoate
20:3(8,11,14)
Desaturase
Arachidonate
20:4(5,8,11,14)
Plant Cell Wall
 They are not chemically homogeneous but composed of several
different materials
 They are not physically homogeneous but built up of distinct
layers
 The most important (90%) component of all plant cell walls of
dicotyledonous are polysaccharides and about 10% is lignin,
protein, water and incrusting substance
 In monocot, the primary wall (the wall initially formed after the
growth of cell consists of 20-30% cellulose, 25% hemicellulose,
30% pectin, and 5-10% glycoprotein; when the cells reach its
final size , the secondary wall consists mainly of cellulose, is
added to the primary wall
 Lignin which is a complex, highly ramified polymer of
phenylpropane residues
Polysaccharides
 Micro-fibril polysaccharides
1. Cellulose (plant cell wall)
2. Chitin (fungi cell wall)
3. Β-1,4-mannans (green algae cell wall)
4. Β-1,3-xylans (green algae cell wall)
 Matrix polysaccharides
1.
Hemicellulose
2. Pectins
Cellulose
 The most abundant organic substance on earth, representing
about half of the total organically bound carbon
 An unbranched polymer consisting of D-glucose molecules which
are connected to each other by glycosidic (β1→4) linkage
 Each glucose unit is rotated by 180° from its neighbor, so that
very long, straight chains can be formed with a chain length of
2000-8000 glucose residues
 About 150 cellulose chains are associated by inter-chain
hydrogen bonds to a crystalline lattice structure known as a
microfibril
Plant cell wall
micro-fibril
 Cellulose micro-fibrils
consisted of about 36 chains
of cellulose, a polymer of
b(14)glucose
 These crystalline regions are
impermeable to water
 Micro-fibrils have unusual
highly tensile strength, very
resistant to chemical and
biological degradation. They
are very difficult to hydrolise
Plant cell wall
micro-fibril
 Many bacteria and fungi
have cellulose-hydrolysing
enzymes (cellulase)
 These bacteria can be found
in the digestive track of
some animals enabling them
to digest grass and straw
Hemicellulose
 A group of polysassharide which were relatively easily
extracted from various plant tissues
 It can be extracted by alkaline solution
 The name is in corrected, it thought to be a precursor of
cellulose (half built cellulose)
 it consists of a variety of un-branched polysaccharides
which contain D-glucose, hexose and pentose
 3 subgroups: xylans, mannans and galactans
Pectin
A mixture of polymers from sugar acids such as
D-galacturonic acids, which are connected by (α1→4) glycosidic links
Some of the carboxyl groups are esterified by
methyl groups
The free carboxyl groups of adjacent chains are
linked by Ca and Mg
Lignin
 An important constituent of the cell wall of xylem
 Lignification of the cell wall occurs after the lying down
of the polysaccharides component of the walls and
towards the end of growing period of the cells
 The distribution of lignin in the wall is not uniform
 Lignin strengthen the wall by forming a ramified network
throughout the matrix, thus anchoring the cellulose
micro-fibril more firmly and protect the micro-fibrils of
the wall from chemical, physical and biological attack
Cellulose biosynthesis
1. It is formed at the outer
surface of the plasmalemma
2. Cellulose is synthesized by
terminal complexes or
rosettes, consisting of
cellulose synthase and
associated enzymes.
Terminal complex (rosette)
Cellulose synthase
Cellulose synthase has not been isolated in its
active form, but from the hydropathy plots
deduced from its amino acid sequence it was
predicted to have eight trans-membrane
segments, connected by short loops on the
outside, and several longer loops exposed to the
cytosol.
Initiation of new
cellulose chain
synthesis
Glucose is transferred from
UDP-glucose to a
membrane lipid (probably
sitosterol) on the inner
face of the plasma
membrane.
New cellulose chain
synthesis (1)
Intracellular cellulose synthase adds
several more glucose residues to the
first one, in (b14) linkage, forming a
short oligosacchairde chain attached to
the sitosterol (sitosterol dextrin).
New cellulose chain
synthesis
Next, the whole sitosterol dextrin
flips across to the outer face of
the plasma membrane, where
most of the polysaccharide
chain is removed by endo-1,4β-glucanase.
New cellulose chain
synthesis
The dextrin primer
(removed from
sitosterol by endo-1,4β-glucanase) is now
(covalently) attached to
another form of
cellulose synthase.
New cellulose chain synthesis
The UDP-glucose used for
cellulose synthesis is
generated from sucrose
produced from
photosynthesis, by the
reaction catalyzed by
sucrose synthase (this
enzyme is wrongly
named).
New cellulose chain synthesis
(5)
• The glucose associated
with UDP is a-linked.
• Its configuration will be
converted by
glycosyltransferases so
the product (cellulose) is
β-linked.
Matrix polysaccharides
• They are synthesized in the cisternae of the golgi
bodies
• Synthase enzymes catalyze the formation of pectin
and hemicellulose