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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