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SHIKIMIC ACID PATHWAY - PowerPoint PPT Presentation


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SHIKIMIC ACID PATHWAY 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

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Presentation Transcript
slide2

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

slide3

GLUCOSE

ORIGINS OF THE

SHIKIMIC ACID

PATHWAY

pentose

phosphate

pathway

glycolysis

Erythrose-4-phosphate

PEP

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

slide4

FORMATION OF SHIKIMIC ACID

phosphoenol pyruvate

B:

H+

erythrose-4-phosphate

H+

H+

NADPH

shikimic acid

slide5

FORMATION OF CHORISMIC ACID

hydrolysis

of PEP

ATP

H+

shikimic acid

pyruvic acid

nucleophilic

addition to C=O

:B

- H3PO4

- H2O

chorismic acid

slide6

PREPHENIC ACID

chorismic acid

Claisen Type

Rearrangement

prephenic acid

pseudoaxial conformation

Prephenic acid can be converted to phenylpyruvic acid

or to 4-hydroxyphenylpyruvic acid:

NADPH

NADP+

p-hydroxy-

phenylpyruvic

acid

phenypyruvic

acid

-H-

-OH

-H+

- CO2

-H+

- CO2

phenylalanine

tyrosine

slide7

CLAISEN REARRANGEMENT

A THERMAL REARRANGEMENT

H+

heat

enolization

an allyl ether

an allyl phenol

slide8

PREPHENIC ACID TO PHENYLALANINE

:B-Enz

- CO2

phenylpyruvic acid

- H2O

prephenic acid

H+

transamination

phenylalanine

slide9

PREPHENIC ACID TO TYROSINE

:B-Enz

- CO2

4-hydroxyphenyl-

pyruvic acid

NAD+

prephenic acid

transamination

hydride transfer

to NAD+

tyrosine

slide10

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.

slide12

Shikimate

Pathways

SHIKIMIC ACID

CHORISMIC ACID

(+ acetogenin piece)

PHENYL-C3

COMPOUNDS

PREPHENIC

ACID

FLAVONOIDS

CINNAMIC

ACIDS

TYROSINE

PHENYLALANINE

PHENYL-C1

COMPOUNDS

ALKALOIDS

ALKALOIDS

slide14

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

slide15

SOME NATURALLY-OCCURING CINNAMYL COMPOUNDS

CINNAMIC

ACID

p-coumaric acid

caffeic acid

ferulic acid

corresponding

aldehydes are

also found -

see next slide

p-coumaryl

alcohol

coniferyl

alcohol

sinapyl

alcohol

sinapic acid

slide16

TYPICAL REDUCTION SEQUENCES

HSCoA

NADPH

NADPH

sinapic acid

sinapyl aldehyde

sinapyl alcohol

estragole

(methylchavicol)

anethole

slide17

CLEAVAGE TO

PHENYL-C1 COMPOUNDS

slide18

CLEAVAGE TO PHENYL-C1 COMPOUNDS

HSCoA

H2O

NADP+

:

ferulic acid

reverse

Claisen

H2O

H2O

reverse

aldol

vanillic acid

vanillin

slide20

FORMATION OF COUMARINS

hydroxylase

isomerization

lactone

(ester)

umbelliferone

coumarin

aesculetin

slide21

DICOUMAROL AND WARFARIN

:

..

- H2O

cinnamic acid

RODENTICIDE

(rat poison)

dicoumarol

causes internal

bleeding in cows

(sweet clover)

Warfarin

anti-coagulant

slide22

FLAVONOIDS

Plant Pigments

slide23

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 don’t 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.

slide24

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

slide25

Anthocyanin

Flower Pigments

slide26

Anthocyanin Leaf Pigments

Autumn Leaves

In Spring and Summer

chlorophyll (green) masks

the anthocyanin colors.

slide27

ANTHOCYANIDINS AND ANTHOCYANINS

NADPH

O2

naringenin (R=H)

[O]

+

Anthocyanins are

red, violet or blue

pigments.

- 2 H2O

pelargonidin (R=H)

cyanidin (R=OH)

plant flower and

leaf pigments

cyanidin is blue

pelargonidin is pink

ANTHOCYANIDINS

slide28

SUMMARY

REPEAT

slide29

(+ acetogenin piece)

Shikimate

Pathways

SHIKIMIC ACID

FLAVONOIDS

CHORISMIC ACID

ANTHRANILIC

ACID

PHENYL-C3

COMPOUNDS

PREPHENIC

ACID

CINNAMIC

ACIDS

TYROSINE

TRYPTOPHAN

PHENYLALANINE

NEXT

LECTURE

PHENYL-C1

COMPOUNDS

ALKALOIDS

ALKALOIDS

ALKALOIDS