2. Fructose and Galactose metabolism

3. Fructose metabolism Principally in the liver (small intestine, kidney)
Essential fructosuria
Hereditary fructose intolerance
Principally in the liver (small intestine, kidney)
Aldolase B: low affinity for fructose 1-phosphate (→ accumulation of fructose 1-phosphate in the liver )

4. The polyol pathway
Seminal vesicles (spermatozoa use fructose)
Accumulation of sorbitol in diabetic patients
Lens (diabetic cataract)
Muscles, nerves (periferal neuropathy)

5. Galactose metabolism:

6. Lens metabolism:
Diabetic cataract :
↑glucose concentration in the lens → ↑aldose reductase activity → sorbitol accumulation → ↑osmolarity, structural changes of proteins

7. Clinical correlations:
A newborn: failure to thrive, vomiting and diarrhea after milk
galactosemia (Galactose 1-phosphate uridylyltransferase deficiency)
genetic disease (AR, 1/60 000)
hepatomegaly, jaundice, cataracts, mental retargation, death
Management: early diagnose, elimination of galactose from the diet (artificial milk from soybean hydrolysate)

8. Summary:
Fructose and Galactose metabolism
Conversion to intermediates of glycolysis
Genetic abnormalities, accumulation of intermediates, tissue damage
Accumulation of sorbitol in diabetes

9. Pictures used in the presentation:
Marks´ Basic Medical Biochemistry A Clinical Approach, third edition, 2009 (M. Lieberman, A.D. Marks)
Textbook of Biochemistry with Clinical Correlations, sixth edition, 2006 (T.M. Devlin)

10. Uronic acid Pathway

11. It is another minor alternative pathway for glucose oxidation by which glucuronic acid, ascorbic acid and pentoses are obtained from glucose.
Like HMP shunt, it does not need nor generate ATP.
Site:
In cytosol of many tissues, especially liver, kidney and intestine.

13. Biological importance of Uronic Acid Pathway:
1-Production of UDP-glucuronic acid, which is the metabolically active form of glucuronic acid which enters in:
Synthesis of mucopolysaccharides.
Detoxification by conjugation: UDP-glucuronic acid is used to detoxify steroid hormones, drugs and toxins.
Formation of conjugated bilirubin.
2-Formation of pentoses.
3-Formation of vitamin C in plants and animal except man and guinea pigs.