Pharma gyan Pandit

Biochemistry of vitamin B1

Vitamin B1 (thiamine) and its derivatives serve many roles in the body. It functions primarily as a cofactor to help enzymes perform their molecular reactions. Several well known biochemical reactions in which thiamine plays a crucial component include:

(1) Conversion of pyruvate to acetyl-CoA.

(2) Conversion of α-ketoglutarate to succinyl-CoA in the Krebs cycle.

(3) Conversion of glyceraldehyde-3-phosphate to ribose-5-phosphate.

(4) It is used by the enzyme branched-chain α-keto acid dehydrogenase.

All of these reactions are crucial to human biochemistry. The conversion of pyruvate to acetyl-CoA feeds important molecules into the Krebs cycle, which allows the cell to produce energy.

The conversion of α-ketoglutarate to succinyl-CoA is necessary for the Krebs cycle to continue "spinning". Without vitamin B1 (thiamine) the cycle would slow causing decreased energy production.

Thiamine is also important in the production of NADPH via the pentose phosphate pathway. NADPH plays a crucial role in biochemistry because it donates its electron pairs to numerous anabolic reactions.

The breakdown of branched chain amino acids such as valine, isoleucine, and leucine are also dependent on thiamine. The product that results from the breakdown of these amino acids are α-keto acids. They can also be fed into the Krebs cycle to replete molecules in the pathway that may have been siphoned off for other purposes.

Since thiamine is involved in many energy producing pathways it is found most abundantly in tissues that produce and use lots of energy. These include, but are certainly not limited to, the brain, muscle, and liver. In the United States the recommended daily allowance is 1.1mg for women and 1.2mg for men.