PLP, the active workhorse of B6
Vitamin B6 is absorbed in several forms (pyridoxine, pyridoxal, pyridoxamine) that the body converts into the active coenzyme pyridoxal 5-phosphate (PLP). PLP is one of the most versatile cofactors in metabolism, central to transamination and decarboxylation reactions. That makes it essential for amino acid metabolism, for synthesising neurotransmitters such as serotonin, dopamine, and GABA, and for the first step of heme synthesis.
The diagram emphasises PLP rather than dietary B6 because it is the active form actually doing the enzymatic work across these pathways.
A vitamin where excess has its own toxicity
B6 is unusual among water-soluble vitamins in that chronic high-dose supplementation can cause harm. Sustained intakes well above requirements have been linked to sensory peripheral neuropathy, with tingling and numbness that may only partly reverse on stopping. This makes B6 a case where more is clearly not better.
Deficiency, by contrast, can cause anaemia and neurological symptoms and is sometimes drug-induced. This is general educational information, not medical advice; do not take high-dose B6 long term without guidance from a qualified professional.