piridoksin

Piridoksin, commonly called vitamin B6, refers to a group of chemically related vitamers that include pyridoxine, pyridoxal, and pyridoxamine. The body primarily stores and utilizes the active coenzyme forms pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP). After ingestion, pyridoxine is absorbed in the small intestine and converted in the liver to PLP, which participates in many metabolic processes.

The principal role of PLP is as a coenzyme in a wide range of enzymatic reactions, especially those involving amino acid metabolism. This includes transamination, decarboxylation, racemization, and desulfuration reactions. Vitamin B6 is also important for the synthesis of neurotransmitters (serotonin, dopamine, norepinephrine, gamma-aminobutyric acid), for heme production via δ-aminolevulinic acid synthase, for niacin formation from tryptophan, and for the synthesis of sphingolipids and immune system components. It is obtained from animal- and plant-based foods and is commonly added to fortified cereals.

Dietary sources include fish, poultry, meat, potatoes, bananas, legumes, and fortified cereals. Deficiency is uncommon in developed countries but can occur in chronic alcohol use, certain medical conditions, or poor intake and may cause anemia, dermatitis, glossitis, cheilosis, neuropathy, and mood changes.

The safe upper intake level for adults is 100 mg per day to avoid potential neuropathy from excessive supplementation. Deficiency and toxicity are typically addressed by adjusting diet and, when needed, supervised supplementation. Interactions exist with certain drugs (eg, isoniazid, penicillamine) and increased requirements may occur during pregnancy or certain health conditions.