Glycolysis and Beriberi

Professor. Manandhar Glycolysis and Beriberi One of the important cofactors necessary for the activity of the pyruvate dehydrogenase complex is thiamine pyrophosphate (TPP). TPP is derived from the vitamin thiamine, also called vitamin B 1. The function of TPP in the pyruvate dehydrogenase complex is to destabilize the bond between the carbonyl and carboxyl groups of pyruvate. A deficiency in thiamine results in the disease called beriberi. The oral manifestations of thiamine deficiency include "old rose" colored tongue, some depapillation at the periphery of the tongue, and a deeper than expected red color of the oral mucosa.

Role of Glycolysis and TCA in Energy Production

Glycolysis and TCA are responsible for ATP production for the body. krebs cycle is an important pathway which involves the function of 8 enzymes which are essential for energy production. This pathway is also an important source for biosynthetic which is used in glucogenesis, prodctuon of glucose. This cycle takes place in the matrix of mitochondria of the cell and oxidzes acetyl coA to gain energy and produce CO2. NADH,FADH,NAD+, and FAD+ are other coenzymes that are used and essential in this pathway. The Krebs cycle is controlled to proficiently meet the needs of the cell and other organism.

Cofactors Required for Krebs Cycle Enzymes

Some Krebs cycle enzymes require non-protein cofactors for activity such as thiamine, vitamin B1. Insufficient quantities of this vitamin in the diet leads to decreased activity of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase and a decrease in the ability of the Krebs cycle to meet metabolic demands causing the disease beriberi. The nervous system relies effectively on glucose as its only fuel. However, in most other tissues can use fats as a source of fuel for the citric acid cycle.

Pyruvate's Role in Citric Acid Cycle

The product of aerobic glycolysis, pyruvate, can enter the citric acid cycle only through the pyruvate dehydrogenase complex. In beriberi, the levels of pyruvate and a-ketoglutarate in the blood are higher than normal. The increase in the level of pyruvate in the blood is especially pronounced after the ingestion of glucose.

Diagnostic Indicators of Beriberi

A related finding is that the activities of the pyruvate and a-ketoglutarate dehydrogenase complexes in vivo are abnormally low. The low transketolase activity of red cells in beriberi is an easily measured and reliable diagnostic indicator of the disease.