Glucose metabolism

1. International Medical School
Topic – Galactose Metabolism, Fructose Metabolism and TCA Cycle
Presented by:

2. Galactose Metabolism
• Galactose Uptake
• Galactose is absorbed in the small intestine and transported into cells
through the SGLT1 (Sodium-Glucose Linked Transporter 1) protein.
• Galactose Conversion to Glucose
• Galactose is converted to glucose in a series of enzymatic reactions.
• The first step is mediated by Galactokinase, which phosphorylates
galactose to galactose-1-phosphate.

3. • UDP-Galactose Metabolism
• UDP-Glucose 4-Epimerase converts UDP-Galactose to UDP-Glucose.
• Galactose-1-Phosphate to Glucose-1-Phosphate
• Galactose-1-phosphate uridyltransferase catalyzes the conversion of
galactose-1-phosphate to glucose-1-phosphate.
• Glucose-1-Phosphate to Glucose-6-Phosphate
• Phosphoglucomutase converts glucose-1-phosphate to glucose-6-
phosphate, which can enter glycolysis and be converted to energy.

5. Disease with Enzyme Deficiency
• Galactosemia
• This is a group of rare genetic disorders caused by deficiencies in
enzymes involved in galactose metabolism. There are three types:
GALT (Galactose-1-Phosphate Uridyltransferase) deficiency, GALK
(Galactokinase) deficiency, and GALE (UDP-Glucose 4-Epimerase)
deficiency. Symptoms can include liver damage, cataracts, and
intellectual disability.

7. Fructose Metabolism

8. Fructose Metabolism
• Fructose Uptake
• Fructose is absorbed in the small intestine primarily via the GLUT5
transporter.
• Fructose Conversion to Fructose-1-Phosphate
• Fructokinase phosphorylates fructose to fructose-1-phosphate.
• Fructose-1-Phosphate to Glyceraldehyde-3-Phosphate
• Aldolase B catalyzes the conversion of fructose-1-phosphate to
glyceraldehyde-3-phosphate.

9. • Glyceraldehyde-3-Phosphate to Pyruvate
• Glyceraldehyde-3-phosphate is further metabolized
through glycolysis to produce pyruvate.

11. Disease with Enzyme Deficiency
• Hereditary Fructose Intolerance (HFI)
• This is caused by a deficiency of Aldolase B.
Individuals with HFI cannot metabolize fructose
properly, leading to symptoms like hypoglycemia, liver
damage, and gastrointestinal issues.

12. TCA Cycle

13. TCA Cycle (Tricarboxylic Acid Cycle or Citric
Acid Cycle)
• Overview
• The TCA cycle is a central metabolic pathway that takes place in the
mitochondria.
• It oxidizes acetyl-CoA derived from carbohydrates, fats, and proteins to
produce ATP, NADH, and FADH2.
• Acetyl-CoA Entry
• Acetyl-CoA enters the cycle by combining with oxaloacetate, forming
citrate.

14. • Key Reactions
• Through a series of reactions, citrate is converted to isocitrate, then to α-
ketoglutarate, and subsequently to succinyl-CoA.
• These reactions generate NADH and FADH2.
• Regeneration of Oxaloacetate
• Succinyl-CoA is converted back to oxaloacetate, completing the cycle and
producing ATP and GTP.

16. Disease with Enzyme Deficiency
• Mitochondrial Diseases
• Several mitochondrial diseases can affect enzymes in the TCA cycle,
leading to metabolic disorders. For example, deficiencies in succinate
dehydrogenase or aconitase can disrupt the cycle, causing various
symptoms such as muscle weakness and fatigue.
• Understanding these metabolic pathways and the associated enzyme
deficiencies is crucial for diagnosing and managing related genetic
disorders and metabolic diseases.

17. Thank You