Role of Vitamins

So far we have established that vitamins do not provide energy. However, they help to unlock the energy from macronutrients. They do this by acting as coenzymes at various stages of glycolysis and the TCA cycle. Here a list of vitamins and their role in energy metabolism. 

Thiamin (B1)

  1. Converted to thiamin diphospate (TDP) which is used to convert pyruvate to acety-CoA
  2. Assists in conversion of alpha-ketoglutarate to succinyl-CoA in the TCA cycle

Riboflavin (B2)

  • Used to make FAD which is converted to FADH2 for the electron transport chain (ETC)
  • Used in the conversion of pyruvate to acetyl-CoA
  • Used to make flavin mononucleotide (FMN). FMN is a part of complex I in the ETC which collects electrons from NADH 

Niacin (B3)

  • Used to make nicotinamide adenine dinucleotide (NAD) which is converted to NADH  for the ETC
  • Used in the conversion of isocitrate to alpa-ketoglutarate; alpa-ketoglutarate to succinyl-CoA; and malate to oxaloacetate in the TCA cycle

Pyridoxine (B6)

  • Used to make pyridoxal phosphate (PLP) which is a coenzyme for more than 100 enzymes involved in amino acid metabolism including production of nonessential amino acids from essential amino acids
  • Used in the conversion of pyruvate to alanine and alanine to pyruvate
  • Conversion of methionine, isolucine and valine to succinyl CoA in the TCA cycle 
  • Used in the conversion of glucose to glycogen
  • Used to make fatty-acyl CoA in fatty acid metabolism

Panthothenic Acid (B5)

  • Used to make CoA which is used to make acetyl-CoA and succinyl-CoA for the TCA cycle

Biotin (B7)

  • Used to convert pyruvate to oxaloacetate; an important intermediate in the TCA cycle
  • Participate in the conversion of methionine and isoleucine to succinyly-CoA

Diagram showing entry points of vitamin-based cofactors in glycolysis and the TCA cycle  

Role of Vitamins

Several vitamins are involved in energy metabolism. The role of iodine, chromium, manganese and sulfur are listed below.

Iodine: Use to make thyroid hormones. Thyroid hormones in turn regulates metabolism in cells. That is, they tell cells when to increase or decrease breakdown of nutrients to release energy

Sulfur: A part of thiamin, biotin and CoA which are all cofactors in energy metabolism 

Chromium: Enhances the ability of insulin to transport glucose from the blood to cells 

Manganese: A cofactors for many enzymes used in metabolic processes such as hydrolysis, phosphorylation, decarboxylation, and transamination

Reference: Thompson,&  J., Manore, M., Vaughan, L. (2020). The science of nutrition (5th ed.). New York. Pearson

Courtney Simons
Courtney Simons is a food science professor. He holds a BS degree in food science and a Ph.D. in cereal science from North Dakota State University.
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