Post on 11-Feb-2017
Metabolism of Other Hexoses
Group I ( Roll no. 1 – 50)
Presenters Kyaw San Lin & KK Thwe SunnKaung Kyaw Min & Kay Yu San
Slideshow preparation Kyaw Khan Zaw & Kyaw San Lin
CONTENTSIntroductionFructose metabolismGalactose metabolismMannose metabolismSummaryReferences
INTRODUCTION
Fate of dietary carbohydrates after digestion & absorption – intermediary metabolism
End products of carbohydrate digestion – monosaccharides: hexoses and pentoses
Principle hexoses – glucose, galactose & fructose
80 – 100% of the total amount absorbed from GI tract - glucose
Remaining 20% or less – mannose, galactose & fructose
After absorption, all enter the liver and converted mainly to glucose.
FRUCTOSE
SOURCES Disaccharide sucrose As free monosaccharide
METABOLISM
D-Fructose Fructo- ATP
kinase ↓Fructose-1-P
↓ ↓Glyceraldehyde DHAP
Aldolase B
The entry of fructose into the cells is not insulin dependent.
DISORDERS OF FRUCTOSE METABOLISM
EXCESSIVE FRUCTOSE CONSUMPTIONFructose ↑
Fructose 1-P ↑
Pi ↓ATP
↓
Gluconeogenesis ↓
Hypoglycemia
Protein synthesis ↓
Clotting factors & other
essential proteins ↓
AMP ↑
AMP degrad
ed
Hyperuricaemia
Gout
DHAP ↑
Glycerol 3-P ↑
entry into glycolysis ↑
Pyruvate ↑
Acetyl CoA ↑
Fatty acid ↑
Hypertriacyl-
glycerolaemia
Cholestrol ↑
Hypercholes-
trolemia
Atherogeni
c
ESSENTIAL FRUCTOSURIA
D-Fructose
Fructo- ATPkinase
Fructose-1-P
↓_↑
It is benign and asymptomatic.
HEREDITARY FRUCTOSE INTOLERANCE (FRUCTOSE POISONING)
Fructose-1-P
↓ ↓Aldolase B Glyceraldehyde DHAP
↑
o Autosomal recessive (1:20,000 births)o Symptoms similar to excessive fructose
consumption.o Sucrose & fructose must be removed from the
diet.
FORMATION OF SORBITOL
D-Glucose
NADPH+H+
NADP+
ALDOSEREDUCTASE
(not found in liver) D-
Sorbitol
SORBITOLDEHYDROGENASE
NAD+
NADH+H+
D-Fructose
FORMATION OF SORBITOL Increases in activity as the glucose
concentration rises In tissues that are not insulin-sensitive Fructose and sorbitol in
Lens → Cataract
Peripheral nerves → Neuropathy Renal glomeruli → Nephropathy
GALACTOSE
SOURCE lactose obtained from milk and its products
METABOLISM
in liverEnters glycolysis
in liver
LACTATING MOTHERS
In lactatingmammary gland
If Gal in diet is insufficient
DISORDER OF GALACTOSE METABOLISM
In lactatingmammary glandin liver
Enters glycolysis
If Gal in diet is insufficient
Galactosemiain liver
GALACTOSEMIA
Is a severe disease that is inhirited as an autosomal recessive trait ( 1 in 35,000 birth)
Physiologic consequences are similar to those found in hereditary fructose intolerance
A broader spectrum of tissues is affected.
Vomiting diarrhea occurs and enlarge liver with jaundice is common
GALACTOSEMIA
The accumulated galactose is shunted into side pathways such as that of galactitol production.
Accumulation of galactitol occurs in
lens of the eye → cataract
Liver → liver damage
Nerve → mental retardation
MANNOSE
SOURCES
Vegetables Hydrolysis of mannan gum
There is little mannose in dietary carbohydrates
METABOLISM
Mannose↓ Hexokinase
Mannose 6-P
Phosphomannoseisomerase↓
Fructose 6-P
SUMMARYGlucose
Glucose 6-P
Fructose 6-P
Fructose 1,6-bisphosphate
Dihydroxyacetonephosphate
Glyceraldehyde 3-PFructose
Fructose 1-P
Galactose
Galactose 1-P
Glucose 1-P
Mannose
Mannose 6-P
Glyceraldehyde
glycolysis
REFERENCES Department of Biochemistry: Biochemistry Handbook
Volume 3. University of Medicine Mandalay, 2012. Murray RK, Bender DA, et al: Harper’s Illustrated
Biochemistry, 28th ed. McGraw Hill, 2009. Harvey R, Ferrier D: Lippincott’s Illustrated Reviews:
Biochemistry, 5th ed. Lippincott Williams & Wilkins, 2011.
Bray GA, Nielsen SJ, Popkin BM: Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Am J Clin Nutr 2004;79:537–43.
Glyconutrition ForLife http://www.glyconutritionforlife.org/Science_of_Glyconutrients/Mannose.php accessed at 8 p.m, 23/7/2012.
Medical and healthcare design slides - Templates - Office.com http://office.microsoft.com/en-us/templates/CT010238352.aspx accessed at 8:27p.m.,13/7/2012
THANK YOU!