Pyridoxal

Pyridoxal is one of the vitamers of vitamin B6, alongside pyridoxine and pyridoxamine. It is the aldehyde form of the vitamin and serves as a starting point for the synthesis of the active coenzyme pyridoxal phosphate (PLP). In humans, the different B6 vitamers are interconvertible and are converted to their phosphate forms by specific kinases; pyridoxal is phosphorylated to PLP, the form that carries out most of vitamin B6’s biological functions.

Pyridoxal phosphate acts as a coenzyme for a wide range of enzymes, particularly in amino acid metabolism. It participates in transamination, decarboxylation, racemization, and β- and γ-elimination reactions. PLP-dependent enzymes are essential for the synthesis and breakdown of amino acids, as well as for the production of several neurotransmitters, including gamma-aminobutyric acid (GABA), serotonin, dopamine, and norepinephrine. PLP is also involved in glycogen phosphorylase activity and various other metabolic pathways.

Dietary sources of vitamin B6 include fish, poultry, meat, potatoes, bananas, legumes, and fortified cereals. In the body, pyridoxal is formed or released from these sources and is subsequently converted to PLP, the principal active coenzyme. Vitamin B6 deficiency is uncommon in developed countries but can occur with poor intake, alcoholism, certain medications, or malabsorption, leading to symptoms such as irritability, dermatitis, and neuropathy. Excessive intake of B6 from supplements can cause neuropathy and other adverse effects.