Vitamin B6 is one of the central molecules in the cells of living organisms. Water-soluble vitamin B6 is widely present in many foods, including meat, fish, nuts, beans, grains, fruits, and vegetables. Additionally, B6 is present in many multivitamin preparations for adults and children and is added to foods as a supplement to foods, power bars, and powders.
There are several active compounds or vitamers which fall under the generic B6. These include pyridoxine alcohol, pyridoxal an aldehyde, pyridoxamine, which differs from the first two with an amine group, and a 2,5' phosphate esters. The major esters are the active coenzyme form and are pyridoxal 5'phosphate (PLP) and pyridoxamine 5'phosphate (PMP). The primary form of B6 in meats are the esters, and the dominant plant source is pyridoxine, which is less bioavailable. Pyridoxine is the most common form found in multivitamins.
As a coenzyme, B6 is involved as a co-factor in over 100 enzymatic reactions, including carbohydrate metabolism, amino acid metabolism, particularly homocysteine, gluconeogenesis, glycogenolysis, and lipid metabolism. Vitamin B6 is also involved in the critical functioning of cells. It plays a significant role in transamination, decarboxylation, initial steps of porphyrin synthesis. Pyridoxine has a role in cognitive development through neurotransmitter synthesis, immune function with interleukin-2 (IL-2) production, and hemoglobin formation.
Fetal brain development requires adequate B6, and this continues throughout infancy. Vitamin B6 recommendations are made in accordance with age and life stage with pregnancy and breastfeeding, involving the highest recommended daily allowance.
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