SHIKIMIC ACID PATHWAY

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SHIKIMIC ACID PATHWAY
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THE SHIKIMIC ACID PATHWAY
This pathway (unique to plants) leads to the
formation of the aromatic amino acids
phenylalanine and tyrosine and to the formation
of many other phenyl-C3 compounds.
Phenylpropanoids
Phenyl-C3
Cleavage of the C3 side chain leads to many
phenyl-C1 compounds.
Phenyl-C1
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GLUCOSE
ORIGINS OF THE SHIKIMIC ACID PATHWAY
pentose phosphate pathway
glycolysis
PEP
Erythrose-4-phosphate
Phosphoenol pyruvate
The pentose phosphate pathway is one that
converts glucose into sugars of different
sizes (different numbers of C) by acyl
interchanges. Erythrose is a 4-carbon sugar.
Acetyl-CoA
Shikimic Acid
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FORMATION OF SHIKIMIC ACID
phosphoenol pyruvate
B
H
erythrose-4-phosphate
H
H
NADPH
shikimic acid
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FORMATION OF CHORISMIC ACID
hydrolysis of PEP
ATP
H
shikimic acid
pyruvic acid
nucleophilic addition to CO
B
- H3PO4
- H2O
chorismic acid
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PREPHENIC ACID
chorismic acid
Claisen Type Rearrangement
prephenic acid
pseudoaxial conformation
Prephenic acid can be converted to phenylpyruvic
acid or to 4-hydroxyphenylpyruvic acid
NADP
NADPH
p-hydroxy- phenylpyruvic acid
phenypyruvic acid
- CO2
-H
-H-
- CO2
-H
-OH
phenylalanine
tyrosine
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CLAISEN REARRANGEMENT
A THERMAL REARRANGEMENT
H
heat
enolization
an allyl ether
an allyl phenol
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PREPHENIC ACID TO PHENYLALANINE
B-Enz
- CO2
phenylpyruvic acid
- H2O
prephenic acid
H
transamination
phenylalanine
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PREPHENIC ACID TO TYROSINE
B-Enz
- CO2
4-hydroxyphenyl- pyruvic acid
NAD
prephenic acid
transamination
hydride transfer to NAD
tyrosine
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PHENYLALANINE AND TYROSINE COME FROM A COMMON
SOURCE AND ARE NOT CONVERTED
PREPHENIC ACID
phenylpyruvic acid
4-hydroxyphenylpyruvic acid
X
tyrosine
phenylalanine
Although most plants could convert phenylalanine
to tyrosine using hydroxylases, this conversion
is a minor pathway. Most plants make enough
tyrosine without converting phenylalanine.
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A PRELIMINARY OVERVIEW
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SHIKIMIC ACID
Shikimate Pathways
CHORISMIC ACID
( acetogenin piece)
PHENYL-C3 COMPOUNDS
PREPHENIC ACID
FLAVONOIDS
CINNAMIC ACIDS
TYROSINE
PHENYLALANINE
PHENYL-C1 COMPOUNDS
ALKALOIDS
ALKALOIDS
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CINNAMYL COMPOUNDS
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CINNAMYL COMPOUNDS
The rings can have various numbers of hydroxyl or
methoxyl groups (hydroxylases and SAM).
NADPH
cinnamaldehyde
NADPH
- H2O
Enz-SH
oxidative cleavage
FADH2
cinnamic acid
benzaldehyde
hydrocinnamic acid
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SOME NATURALLY-OCCURING CINNAMYL COMPOUNDS
CINNAMIC ACID
p-coumaric acid
caffeic acid
ferulic acid
corresponding aldehydes are also found - see next
slide
sinapic acid
p-coumaryl alcohol
coniferyl alcohol
sinapyl alcohol
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TYPICAL REDUCTION SEQUENCES
HSCoA
NADPH
NADPH
sinapic acid
sinapyl alcohol
sinapyl aldehyde
estragole (methylchavicol)
anethole
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CLEAVAGE TO PHENYL-C1 COMPOUNDS
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CLEAVAGE TO PHENYL-C1 COMPOUNDS
H2O
HSCoA
NADP

ferulic acid
reverse Claisen
H2O
H2O
reverse aldol
vanillic acid
vanillin
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COUMARINS
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FORMATION OF COUMARINS
isomerization
hydroxylase
lactone (ester)
umbelliferone
coumarin
aesculetin
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DICOUMAROL AND WARFARIN

..
- H2O
cinnamic acid
RODENTICIDE
(rat poison)
dicoumarol
causes internal bleeding in cows
(sweet clover)
Warfarin
anti-coagulant
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FLAVONOIDS
Plant Pigments
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PLANT PIGMENTS
Flavonoids and anthocyanins are conspicuous plant
pigments in nature that are responsible for the
beauty and splendor of flowers, fruits, fruit
tree blossoms and of the autumn
leaves. Flavones are responsible for the yellow
and orange colors and the anthocyanins are the
source of red, violet and blue colors. These
compounds occur mainly in higher plants and are
less common in the lower orders. You dont find
them in algae, fungi or bacteria. The flavonoids
play a major role in attracting insects to feed
and pollinate these plants. Some of them also
have a bitter taste and repel harmful insects
like caterpillars. Flavonoids are thought to be
antioxidants, and play a major role in our diet,
preventing the ravages of aging caused by
free-radicals. These compound have their
biosynthetic origin in both the skimic acid
pathway and the acetogenin pathway - they are of
hybrid origin.
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shikimic acid pathway
NARINGENIN
found in grapefruit
A different starter than acetyl-CoA.
malonyl-CoA 3x
acetogenin pathway

Michael addition
internal Claisen and enolizations
MIXED-ORIGIN COMPOUND
A FLAVONE
flavones are yellow or orange pigments
naringenin
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Anthocyanin Flower Pigments
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Anthocyanin Leaf Pigments
Autumn Leaves
In Spring and Summer chlorophyll (green)
masks the anthocyanin colors.
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ANTHOCYANIDINS AND ANTHOCYANINS
NADPH
O2
naringenin (RH)
O

- 2 H2O
Anthocyanins are red, violet or blue pigments.
pelargonidin (RH) cyanidin (ROH)
plant flower and leaf pigments
cyanidin is blue pelargonidin is pink
ANTHOCYANIDINS
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SUMMARY
REPEAT
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( acetogenin piece)
SHIKIMIC ACID
Shikimate Pathways
FLAVONOIDS
CHORISMIC ACID
ANTHRANILIC ACID
PHENYL-C3 COMPOUNDS
PREPHENIC ACID
CINNAMIC ACIDS
TYROSINE
TRYPTOPHAN
PHENYLALANINE
NEXT LECTURE
PHENYL-C1 COMPOUNDS
ALKALOIDS
ALKALOIDS
ALKALOIDS