Monosaccharides

(Structure and biological function)

Ďuračková Zdeňka

Institute of Medical chemistry, Biochemistry and Clinical

Biochemistry,

Comenius University

Medical Faculty

E

5m

76 800 kJ

Importance

• Source of energy

glucose, glycogen, starch

• Structural function

connective tissue, membranes

nucleic acid

• Recognitive function

cytoplasmic membranes

receptors

PHOTOSYNTHESIS

6CO2 + 6H2O C6H12O6 + 6O2 + heat energy

H2O O2

Saccharides formation

CO2

C6H12O6

Light energy

chlorophylEnergy transport

NADP+ NADPH + H+

ATP

+

Monosaccharides

(1 unit)

Polysaccharides

(more than 10 units)

Oligosaccharides

(2 – 10)

Saccharides

Monosaccharides

• Triózy – C3 - Trioses

• Tetrózy – C4 - Tetroses

• Pentózy – C5 - Pentoses

• Hexózy – C6 - Hexoses

• Polyhydroxyaldehydes

- OH, - CHO

• Polyhydroxyketons

- OH, >C=O

Saccharides - Sacharidy

CnH2nOn

• Trioses C3H6O3

• Tetroses C4H8O4

• Pentoses C5H10O5

• Hexoses C6H12O6

Properties of monosaccharides

• Soluble in water

Insoluble in organic solvents and lipids

• Nonelectrolytes

They do not disociate in water

• Sweet taste

Functional isomers

Aldose Ketose

C3H6O3

Epimers

• Different possition of one secondary -OH

C H O

O H

H O

O H

O H

C H2O H

C H O

H O

O H

O H

C H2O H

H O

C H O

O H

H O

H O

O H

C H2O H

C H O

O H

O H

C H2O H

O H

C H O

O H

C H2O H

O H

H O

D-glucose D-manose D-galactose

C2 epimer

C4 epimer

D-ribose D-arabinose

Optical isomers

*

Subject and picture in the mirror

Enanthiomers (D-,L- isomers) C6H12O6

Difference in the

possition of all

secondary

- OH groups

Responsibility for D- a L-classification =>

The last

asymetric carbon

*

*

*

*

Cyclic monosaccharides = hemiacetals

H

R - C = O + HO – R R – C - OH

O – R

H

HemiacetalReaction of hemiacetal formation

Aldehyde Alcohol

Cyclic monosaccharides = hemiacetals

O

OH

OH

O

Tollens projection

Fischer projection

H-C=O

H-C-OH

HO-C-H

H-C-OH

H-C-OH

CH2-OH

*

*

*

*

Anomers

+ 52,7

+ 112 + 18,7

Cyclisation of glucose

Noncyclic form Cyclic form

Noncyclic and cyclic form of FRUCTOSE

Noncyclic form Cyclic form

Cyclic forms cyclic hemiacetals

heterocycle with O - pyranose or furanose

Cyclic forms of monosaccharides

pyran O

furan

O Opyranose furanose

Mutarotation

The ability of organic compounds in solution to

change the optical rotation about a certain angle

-D-glucose - 112o - 36,5 %

-D-glucose - 19o - 63,5 %

Final rotation - 52,7o

Mutarotation is consequence of

anomerisation

α-D-glucopyranose

36,5 %β-D-glucopyranose

63,5 %

112° 19°

Final rotation 53,9 °

H2O

Important monosaccharides

D – Glucose

• the most extended in naturebuilding unit of starch, glycogene and cellulose

• concentration in blood 3,3-5,5mmol/l

regulation by insulin and glucagon

patolog.state: diabetes mellitus

• source of energy (especially for brain and erythrocytes)

C

C

C

C

C

CH2OH

OH

OHH

HHO

OHH

OHH

D - galactose

• epimer of glucose – different configuration at C-4

• linked - in lactose (disaccharid)

- building part of glykoproteins, glykolipids

C

OH

CH OH

C HHO

C HHO

C OHH

CH2OH

D – fructose

• the most extended ketose

• free – honey

• linked in saccharose (disacharide)

C

C

C

C

O

HHO

OHH

OHH

CH2

CH2OH

OH

C

C

C

C

O

HHO

OHH O

H

H

CH2

CH2OH

OH

D- alpha - fructose

D - ribose and D - 2 - deoxyribose

• pentoses

• building units of nucleic acids

O

HH

H

H

OH

H

OHH2CHO

2-deoxyribosa

C

C

C

C

CH2OH

OHH

OHH

OHH

OH

C

C

C

C

CH2OH

HH

OHH

OHH

OH

Ribose 2-deoxyribose

Phosphate ester formation

R OH + HO P OH

O

OH

R O P OH

O

OH

+ H2O

Alcohol Phosphoric acid Phosphate ester

Phosphate esters of monosaccharides

Cori’s ester Robison’s ester

Neuberg’s ester

1947 Nobel price1

1 1

6

1

6

6

Nobel price in physiology a medicine 1947

Gerty Teresa Cori (1896 Prague -1957 USA)

Biochemst and medical doctor, 1920 – Prague

University – she lived in the USA

Carl Ferdinand Cori (1896 Prague – 1984 USA)

Biochemist and medical doctor

Nobel prize (1947) "for their discovery of the

course of the catalytic conversion of glycogen”

Together with Bernardo Alberto Houssay for

discovery of hormones participation in metabolism

of saccharides

Glucose – 1 – P

Robison Robert (1883-1941), biochemist,

England

6

1

In 1923 he announced the discovery of the

enzyme phosphatase in aqueous extracts of

bones of young, rapidly growing animals.

He published a volume on the significance of

phosphoric esters in metabolism in 1932.

Neuberg ester Carl Alexander Neuberg (1877–1956) reffered to as

"Father of Biochemistry".

6

He studied chemistry of carbohydrates,

amino acids, enzymes and fermentation

Aminosaccharides

Sialic acids

- NH2 substitution:

•acetyl

•glycolyl

-OH substitution:

•acetyl

•lactyl

•sulphate

•fosphate

Deoxysaccharides

-D-ribose -D-2-deoxyribose

Enolisation

D-glucose D- manose

D-fructose

Reduction of

monosaccharides

C

CH2

OHOH

OHOH

OH

H O

CH2

OHOH

OHOH

CH2 OH

OH

red.

(+ 2 H)

CH2

OOH

OHOH

CH2 OH

OH CH2

OHOH

OHOH

CH2 OH

OH

D- glukóza D- glucitol

D- manitolD- fruktóza

red.

red.

(+ 2 H)

(+ 2 H)

HO

HO

HO

HOHO

D - glucose

D - Fructose

Oxidation of glucose

Glucuronic acid Glucaric acid

Gluconic acid

Glucose

Uronic acid Aldonic acid Aldaric acid

X

X

1

1

6

6

UDP - glucose

Oxidation of glucose

in the organism

UDP-glucose

UDP-glucuronic acid

1

6

Oxidation of UDP-glucose to UDP-glucuronic acid

The function of glucuronic acid

• Detoxication of aromatic compounds

• Substrate for ascorbic acid synthesis

Detoxication

function of

glucuronic acid

O

COO-

OH

OH

OH

O

OH

O

P H2CO

OH

P

OH

O

O

O

OH OH

HN

N

O

O14

UDPGlcU

UDPGlcU UDP

UDP- glukoziduronáttransferáza

GlcU O

REAKCIA S FENOLOM, VZNIKÁ O-GLUKOZIDURONÁT

REAKCIA S KYS. BENZOOVOU A SALICYLOVOU, VZNIKAJÚ ESTERY

COOHUDPGlcU UDP

UDP- glukoziduronáttransferáza

GlcU O C O

REAKCIA S ANILÍNOM, VZNIKÁ N-GLUKOZIDURONÁT

NH2UDPGlcU UDP

UDP- glukoziduronáttransferáza

GlcU NH

Bilirubin – degradative product of hem

Elimination of bilirubin from the organism

• Trap 1O2

• It secures vitamin A before autooxidation

• Inhibition of linolic acid oxidation

• Scavenger of peroxyl radicals

• Inhibition of carbonylprotein formation

• Elimination of HOCl

• Synergistic activity with vitamin E

Biological functions of ascorbic acid

• Co-factor of enzymes – hydroxylases

• Reductant (Fe(III) Fe(II), Cu(II) Cu(I))

• Reduction of nitroso-compounds to nontoxic form

• Scavenger of superoxide, .OH, R

.

Synthesis of ascorbic acid

O = C

HO – CH

HO – CH

HO – CH2

HC

O

HO – CH

L-gulono-

lacton

L-gulonoic

acid

D – glucuronic

acid

COOH

HO – CH

HO – CH

HO – CH2

HC – OH

HO – CH

+ 2H

L-gulonolacton dehydrogenase

O

=O

OH OH

CH2 – OH

HO – CH

L-ascorbic

acid (vitamín C)

- 2H

51

+ H2O 2

Non-enzymic

glycation of

proteins

C

CH2

OHOH

OHOH

OH

H O

D- glukóza

H2N proteín+

CH2

OHOH

OHOH

OH

CH N proteín

aldimín

(Schiffova zásada)

CH2

OOH

OHOH

OH

CH2 NH proteín

ketoamín

(fruktózamín)

- H2OHO

HO

HOD-glucose

protein

Aldimine

Schiff base

Ketimine

(fructosamine)

Glycosides formation

Sach-OH HO-Sach+ Sach-O-Sach

hologlycosid

Sach-OH + HO-R Sach-O-R

O -heteroglycosid

Sach-OH + HN< Sach-N<

N -heteroglycosid

Important disaccharides

Maltose

• present in malt, enzymatic hydrolysis of starch in intestine

• 2 molecules of glucos - -1,4 glycosidic bond

- maltosa

Lactose

• „milk saccharid“

• galactose and glucose, -1,4 glycosidic bond

• milk : kow 4-6%

women 6%

• less sweet than saccharose

Saccharose

Glc-(1 2)-Fru

-glucose unit -fructose unit

Saccharose

• „beet sugar, cane sugar“

• glucose and fructose, α – (1 - 2) glycosidic bond

ß

21

X-ray analysis of crystallic sugar from shop

Real structure of saccharose

Cellobiose

• building unit of cellulose

• 2 molecules of glucose, - 1,4 glycosidic bond

- celobiosa

Sweetness of various compounds

Name Type of compound Sweetness

Lactose Disaccharide 0.16

Maltose Disaccharide 0.33 – 0.45

Sorbitol Polyalcohol 0.6

Glucose Monosaccharide 0.74 – 0.8

Sucrose Disaccharide 1.00 (reference)

Fructose Monosaccharide 1.17 – 1.75

Sodium cyclamate Sulfonate 26

Steviol glycoside Glycoside 40 – 300

Aspartame Dipeptide methyl ester 180 – 250

Sodium saccharin Sulfonyl compound 300 – 675

Thaumatin Protein 2000

Sweetness of sugars