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Physiological Role of Thiamine
- The biologically active form of Thiamine is known as Thiamine pyrophosphate or TPP.
- It acts as a Coenzyme in the following reactions:
1. Pyruvate dehydrogenase
- Thiamine pyrophosphate (TPP) is used in oxidative decarboxylation of alpha keto acids, e.g. pyruvate dehydrogenase catalyzes the breakdown of Pyruvate, to Acetyl CoA, and carbon dioxide.
2. Alpha ketoglutarate dehydrogenase
- Another similar biochemical reaction that requires TPP is the Oxidative decarboxylation of alpha ketoglutarate to succinyl CoA and CO2 in Citric acid cycle.
- The second group of enzymes that use TPP as co-enzyme are the transketolases in the Hexose monophosphate shunt pathway (HMP) of glucose.
- The main role of Thiamine pyrophosphate (TPP) is in carbohydrate metabolism.
- So, the requirement of Thiamine is increased along with higher intake of carbohydrates.
Deficiency Manifestations of Thiamine
- The oxidative decarboxylation of Pyruvate and alpha ketoglutarate play a major role in energy metabolism of most of the cells especially in the tissues of the nervous system.
- In Thiamine deficiency, the activity reactions that are catalyzed by the two dehydrogenases is decreased.
- This results in the decreased production of ATP and impaired cellular function.
- The deficiency of Thiamine may be manifested as a disease called as Beriberi.
- Beriberi is a severe Thiamine deficiency syndrome found among Asians where rice is a staple food, especially if eating well-polished rice where Thiamine has been removed.
- Early symptoms are anorexia, dyspepsia, heaviness and weakness.
- The early symptoms are anorexia, dyspepsia, heaviness and weakness.
- Subjects feel weak and get easily exhausted.
- Different types are:
- Wet Beriberi
- Dry Beriberi
- Infantile Beriberi
- Wernicke-Korsakoff Syndrome
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