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Saccharides
(Structure and biological function)
for dentistry
Ďuračková Zdeňka
Departemnt of Medical chemistry, Biochemistry
and Clinical Biochemistry,
Komenius University
Medical Faculty
Importance
• Source of energy
glucose, glycogen, starch
• Structural function
connective tissue, membranes
nucleic acid
• Recognitive function
cytoplasmic membranes
receptors
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 – enanthiomers – stereoisomers
*
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
H-C=O
H-C-OH
HO-C-H
H-C-OH
H-C-OH
CH2-OH
Tollens projection
Fischer projection
Anomers
+ 52,7
+ 112 + 18,7
Anomers formation from fructose
and glucose
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
Aminosaccharides
Sialic acids
- NH2 substitution:
•acetyl
•glykolyl
-OH substitution:
•acetyl
•laktyl
•sulfát
•fosfát
Enolisation
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
Oxidation of glucose
Glucuronic acid Glucaric acid
Gluconic acid
Glucose
Uronic acid Aldonic acid Aldaric acid
1
1
6
6
Oxidation of glucose
Glucuronic acid Glucaric acid
Gluconic acid
Glucose
Uronic acid Aldonic acid Aldaric acid
X
X
1
1
6
6
Oxidation of UDP-glucose to UDP-glucuronic acid
X
The function of glucuronic acid
• Detoxication of aromatic compounds
• Substrate for ascorbic acid synthesis
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
.
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
HO
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
• malt, enzymatic hydrolysis of starch in intestine
• 2 molecules of glucose - -1,4 glycosidic bond
• free hemiacel group is present – reducing disaccharide
- maltosa
Lactose
• „milk saccharid“
• galactose and glucose, -1,4 glycosidic bond
• milk : cow 4-6%
women 6%
• less sweet than saccharose
• free hemiacel group is present –
reducing disaccharide
Saccharose
• „beet sugar, cane sugar“
• glucose and fructose, – 2,1 glycosidic bond
•no free hemiacetal group is present – non-reducing
disaccharid
Cellobiose
• building unit of cellulose
• 2 molecules of glucose, - 1,4 glycosidic bond
- celobiosa
Polysaccharides
• Homopolysaccharides
(one kind of monomeric unit)
• Heteropolysaccharides
(two or more different monomeric units)
Homopolysaccharides
• Polyglucan (starch, glycogen)
• Polygalactan (agar)
• Polyfructan (inuline)
Starch
• lat. amylum, angl. starch, greec amylo
• storage polysaccharides of plants
• The main sorce of energy
• Formed from D-glucoses
• In water at higher temperature coloidal solution
• Different numbers of monosaccharid units
The composition of starch
Amylose• 20-30 %
• -1,4 bonds
• linear (helix)
• Soluble in water
• Amylase is cleaved to
maltose
Amylopectine
• 70-80 %
• -1,4 + -1,6 bonds
• branching
• Insoluble in water
• Amylase is cleved in
maltose + dextrins
Amylose
O
OO
HO
OH
O
O
HO
OH
O
H
H O
OO
HO
OH
O
O
HO
OHH
H
14
Amylopectine
O
OO
HO
OH
O
O
HO
OH
O
H
H
O
OO
HO
OH
O
O
HO
OH
O
H
H O
OO
HO
O
O
HO
OHH
H
14
1
6
Glycogen
• Storage polysaccharid in animals
• Similar as amylopectine, branching is more
frequent
• Bonds -1,4 + -1,6
• The accurrence in food is low
(liver, horse meet)
Branching in glycogene
····
· · ·
α-1,4
α-1,6
Cellulose
• The most expanded polysaccharide in plants
• composed from D-glucose,
• bonds -1,4
• linear chains layed paralel and fixed with
hydrogen bonds,
• The consequence – strenght and water insolubility
Cellulose
O
OH
HOO
OH
O
OH
HO O
OH
O
OH
HOO
OH
O
OH
HO
OH
1
4
ß
HETEROPOLYSACCHARIDES
(heteroglykans)
(derivSach-O-derivSach)n
Examples of derivatives of
monosaccharides present in
heteropolysaccharides
Glucosamine
D-Glucuronic acid
L-Iduronic acid
HETEROPOLYSACCHARIDES
(Mucopolysaccharides)
2 different monomers
(6 classes)
Chondroitinsulphate (GUA + GAL-NAc-SO4)n
Darmatansulphate (IdUA + GAL-NAc-SO4)n
Keratansulphate (GAL + GNAc-SO4)n
Heparinsulphate (IdUA-SO3H + GNAc -SO4)n
Heparine (GUA + GNAc-SO4)n
Hyaluronate (GUA + GNAc)
(no sulphate)
Glykolipids
Proteoglycans
Glykoproteins
Glycoconjugates
Basic glycosaminoglycan is
hyaluronic acid
Glucuronic acid +
N-acetylglucosamine
1934 - Karl Meyer – from cows‘ eyes - in an
ophthalmology laboratory at Colombia
University
1942 - Endre Balazs - from rooster combs –
HA had been injected as a serum into the
arthritic knees
Basic disaccharide
Structure of hyaluronic acid (HA)
1
4OO
OH
HO O
O
NH
O
OH
HO
COCH3
COO
13
COOO
OH
HO O
In human body – 15 g of HA
One third is metabolised daily (degradated and
synthetised)
Hyaluronan has variable molecular weight
Occurence of HA in human body
In the skin
Synovial
fluid
HK – connective tissue
in the gum
In joint In tooth
Occurence of HA in human body
Heparin
• Antiagregation agent of blood in vivo + in vitro
• From animal organs is prepared
• Prevention and treatment of thrombosis, after IM,
during surgery performance, etc. = antithrombic
effect
• Preparation of noncoagulated blood for
laboratory and transfusion use = anticoaguland
(Glucuronic acid + NacetylGlucose-sulphate)
Glycoconjugates
Saccharide unit and non-saccharide unit
linked together
Sacharid OH + HO R
Glycoconjugates
Glycoconjugates
• Glycolipids (saccharid unit + sphingosine)
• Proteoglycans (saccharid unit + protein)
• Glycoproteins (saccharid unit + protein)
Proteoglycans
• contains neer to 95% saccharide units
• D-conformation (except: L-iduronic
acid, L-arabinose, etc)
• H2SO4 linked in high amount
• polyanionic character
• high viskosity – biological lubricant
• high elasticity
• influence of water and ionic equillibrium
• stabilizing and retaining function
Importance of proteoglycans
• Part of connective tissues (bons, gristle, skin, cornea,
venous)
• Water is absorbed - gel (responsible - sulphate and
glucuronic acid)
• Gristel (chrupavka) - colagen repleted by poteoglycans,
pressure stability
Thank you
for your attention .............