metabolic pathways shared by fructose

1. Fructose metabolism

2. Metabolism of fructose
in muscle and extra hepatic
tissue
Fructose
Fructose -6-phosphate
Glucose 6 Phosphate
ATP
ADP
Hexokinase
Pyruvate
Glycolysis
Glycogen
F1,6 BP
Phosphohexose isomerase

3. Metabolism of fructose
in Liver
Fructose
Fructose -1- phosphate
Glyceraldehyde
ATP
ADP
Fructokinase
TAG
Glycero phospholipid
Aldolase B
DHAP
Glycerol 3 P
Alcohol DH
Glycerol
NAD NAD H + H
Glycero kinase
ATP
ADP
Glycolysis
Gluconeogenesis
1
2
3
4
5
6

4. Formation of Sorbitol
D-Glucose
NADPH+
H
+
NADP
+
ALDOSE
REDUCTASE
(not found in liver)
D-Sorbitol
SORBITOL
DEHYDROGENASE
NAD+
NADH+H
+
D-Fructose

5. 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

6. Essential Fructosuria
It is benign and asymptomatic.

7. Hereditary Fructose Intolerance
(Fructose Poisoning)
o Autosomal recessive (1:20,000 births)
o Symptoms similar to excessive fructose consumption.
o Sucrose & fructose must be removed from the diet.

8. Excessive Fructose Consumption
Fructose ↑
Fructose 1-P ↑
Pi ↓
ATP ↓
Gluconeogenesis ↓
Hypoglycemia
Protein synthesis ↓
Clotting factors
& other essential
proteins ↓
AMP ↑
AMP degraded
Hyperuricaemia
Gout
DHAP ↑
Glycerol 3-P ↑
entry into
glycolysis ↑
Pyruvate ↑
Acetyl CoA ↑
Fatty acid ↑
Hypertriacyl-
glycerolaemia
Cholestrol ↑
Hypercholes-
trolemia
Atherogenic

9. Fructose
Fru-1-P
Glyceraldehyde
Glycerol
Glucose
Fru-6-P
DHAP
Glucose 6-P
Fru 1,6-BisP
Glycerol 3-P DHAP
Glyceraldehyde 3-P
PFK F-1,6 bis-P
Hexokinase
ATP
FructokinaseATP
Aldolase B
Triokinase ATP
Glycerol kinase
ATP
DH
Glycogen
NADH+H+
NAD
TAG
pyruvate