Glyc Oc Ides

8/20/2019 Glyc Oc Ides

1/19

Glycosides and Glycosidases

1. Definition

2. Examplesb. Isoprenoid glycosides

- aroma- sweeteners- medicines- molecular biological reagent- anti-fungal saponins- intermediates to primary andsecondary metabolites

(u) (u)

061109

a. Phenylpropanoid glycosides

c. Glucosinolates

d. Indigo

e. Cyanogenic compounds

3. Summary

• Polymer (structure)

Glycosides of phytohormones (auxin, cytokinin),

Isoprenoids, Alkaloids

Phenylpropanoids

Glucosinolates, Cyanogenic glucosides, etc..

• Conjugates (non-structure)

To protein GlycoproteinsTo other chemicals

e.g., Cellulose..(Most abundant chemical on earth)

To nucleotides e.g., ADP-glucose, UDP-glucose

Carbohydrates in Plants

R X Aglycone

N (N-X-S/T); O (S/T)( ER membrane, Golgi)

Glycone


2/19

X = O, N, S, none

R (+OH):

1

2

3

45

6

-Glucose

O

OH

OH

OH

-Rhamnose

O

OHOH

OH

OH

OH

O

OH

OH

OH

OH

OH

-Galactose

Anomeric carbon

R X

“Glycoside”

Aglycone

R X

R-OH

HX

Aglycone

NDP-R

Glycoside

Glycosidase

Glycosyltransferase


3/19

-Glucosidase

O-Glc

NO2

OH

NO2

Abs at 420nm

3. “Substrate specificity”

1.Almond emulsin:

used to determine structure of glycosides

2. Can be detected with a commercially available

substrate


1. Definition


- aroma- sweeteners

- medicines- molecular biological reagent- anti-fungal saponins- intermediates to primary andsecondary metabolites

(u) (u)


c. Glucosinolates

d. Indigo


3. Summary


4/19


5/19


6/19

OH

R1

R2

R3Isoprenoid glycosides

R1 R2 R3

O-Glc-GlcO-Glc-GlcO-Glc-Glc

O-Glc-GlcO-Glc-AraO-Glc

H

HH

OHOH

O-GlcO-Glc-Rha

OH O-Glc-Rha

OH O-Glc-Rha

O-GlcOHO-GlcOH

Protopanaxadiol saponins

Protopanaxatriol saponins

Panax ginseng

Cardiac glycosides

O

O O

OH

O

OH

O

OH

OO

OH

OOH

Digitoxin

O

O O

OH

O

OH

O

OH

OO

OH

OOH

OH

Digoxin

Digitoxigenin

Digoxigenin

Isoprenoid glycosides

Digitalis purpurea

(Foxglove)

(DIG)digitoxose

Inhibit the membrane bound Na+-K+-ATPase pump

Increase contraction (+ inotropic effect)

of the heart


7/19

Dioscorea spp. (wild yam)

https://reader012.{domain}/reader012/html5/0808/5b6a18f201c5c/5b6a18f8bc955.jpg

http://www.rain-tree.com/Plant-Images/dioscorea-pic.htm

O

O

OH Diosgenin

O

O

Progesterone


O

O

R1O

O

R1O

O

Glc

OH

Furostanol glycosides

(in fresh plants)

Spirostanol glycosides

(in harvested plants)

R1 = mono- or oligosaccharide

Antifungal activity“Harmless”


Furostanol glycosde 26-O-β-glucosidase (F26G)

O

O

OH Diosgenin= “Saponin activating enzyme in plants”


8/19


1

5

67

8

4

Substrates

Enzyme

O

O

R1O

O

R1O

O

Glc

OH



9/19

O

O

N

O

CHO

OH

CH2OH

O AraGlc

Glc Avenacin

Avenacinase

Bowyer et al., ’95 Science 267:371-374

Ggt, Gaeumannomyces graminis var. tritici

Gga, Gaeumannomyces graminis var. avenae


Alkaloid glycosides

= “Saponin INactivating enzyme in fungi”

Most steroid glycosides (saponins)

are believed to exist in vacuolesO

O

R1O

OH

R1

R2

R3

H

H

H

O

O

O

OHO

OH

OHOH

OH

HOOC

COOH

O

O O

OH

O

OH

O

OH

OO

OH

OOH

OH



10/19

Glc-O

OH

OH


UDP-GlcUDP

Sterols = membrane components

cholesterol

β-sitosterol

Also in membrane..

(plasma membrane)

One form of phytosterols

OO

OH

OH

OH OH

O

OH

OH OHOHO

O

OH

OH OH

OO

OH

OH

OH OHn

Peng et al., ’02 Science 295:147-50

Read and Bacic ’02 Science 295:59-60



11/19

O

O-Glc

NHNH H H

HO

O

O

O-Glc

H

H

HO

O

O

Secologanin

(monoterpene)

Strictosidine


NH

NH2

tryptamine

Alkaloid glycosides

STR(Strictosidine synthase)

N

N

CO2CH

3

H

OHCH

3

OCH2CH

3MeO

Vindoline

NH

N

CO2CH

3

H

Tabersonine

O

O-Glc

NHNH H H

HO

O

Strictosidine

NH

N

CO2CH

3

H

NHNH H H

HO

O

CHO

CHO

N+

NH H

HO

O OHO

OH

NHNH H H

HO

O

CO2CH

3

N

NH

Tabersonine

16-hydroxytabersonine

NH

N

CO2CH

3

H

OHVindoline

4,21-dehydro-geissoschizine

Various indole alkaloids

SGD

T16H

Isoprenoid glycosides Alkaloid glycosides

(Strictosidine β-glucosidase)


12/19

Vacuole

Nucleus

Chloroplast

Golgi body

Cell wall Plasma membrane

Mitochondrion

Peroxisome

Buchanan et al. (2000) Biochemistry & Molecular Biology of Plants

Endoplasmic

reticulum

Strictosidine

T16HSGD

STR

Young leaves


1. Definition


- aroma- sweeteners

- medicines- molecular biological reagent- anti-fungal saponins- intermediates to primary andsecondary metabolites

(u) (u)


c. Glucosinolates

d. Indigo


3. Summary


13/19

R S C N

R N C S

R C N

S

N

O

NH

S

Glucosinolates

Myrosinase (thio-glucosidase)

C

NO

S Glu

SO3-

R

CN

O

SH

SO3-

R

Isothiocyanate

(mustard oils)

Nitrile

woad

Wild indigo


14/19


15/19

R'C

R O-Glc

CN

R'C

R OH

CN

R'

CR

O HCNSH

HOOCNH

2

HOOCNH

2

CN

HOOCNH

2

CONH2

HOOCNH

2

COOH

Cyanoalaninesynthase

Cyanogenic glycosides

cyanohydrin

HCN

CH O

CN

Glc O Glc

CH O

CN

Glc

Amygdalin

PrunasinMandelonitrile

CH OH

CN

CHO

Benzaldehyde

AH

PH

MDL

..Not so specific..

..Abundant...(5-10% of soluble proteins in seed)


16/19

Immunoblot

Enzyme => Procambium cells Substrate =>

Cotyledonary parenchyma

Poulton and Li, ‘94

+ indican

Tissue printing on nitrocellulose

+ almond

β -glucosidase

Where are the enzyme and the substrate?

+ amygdalin

Hg++ + 2CN-

Hg (ppt) + Hg(CN)2

Cyanogenic glucosides in Hevea

Linamarin Linustatin

CH3

CCH

3 O

CN

Glc O Glc

CH3

CCH

3 O

CN

Glc

Cotyledons

Endosperm

Fully-grown,

immature seed Mature seedSelmar, ‘95

Linamarase

(in apoplast)

HCN


17/19

Cyanogenic glucosides in Hevea

CH3

CCH

3 O

CN

Glc O Glc

Linustatin

Asparagine

Linustatin

*Linamarasein apoplast

Diglucosidase

14C-labeling

CH3

CCH

3 O

CN

Glc

Cyanoalanine

synthase

*Non-specific Selmar, ‘95

*


18/19


1. Definition


- aroma- sweeteners- medicines- molecular biological reagent- anti-fungal saponins- intermediates to primary andsecondary metabolites

(u) (u)


c. Glucosinolates

d. Indigo


3. Summary

-Glucosidases

• Substrate specificity

• Monocot vs. Dicot

Glycosylation

Expression

Location

Transit peptide

Signal peptide


19/19

R X

*Not necessary for alkaloids

R-OH

HX

Aglycone

UDP-R

Glycoside

Glycosidase

Toxicity?

Hydrophobicity?

Reactivity?

Compartmentalization

Glyc Oc Ides

Documents