Pyridoxal phosphate (PLP, pyridoxal 5'-phosphate, P5P), the active form of vitamin B6, is a coenzyme in a variety of enzymatic reactions. The International Union of Biochemistry and Molecular Biology has catalogued more than 140 PLP-dependent activities, corresponding to ~4% of all classified activities. The versatility of PLP arises from its ability to covalently bind the substrate, and then to act as an electrophilic catalyst, thereby stabilizing different types of carbanionic reaction intermediates.

1. Pyridoxal phosphate is a coenzyme of transaminase and decarboxylase in amino acid metabolism. It can promote the decarboxylation of glutamate and increase the production of γ-aminobutyric acid, which is a neuroinhibitory transmitter.
2. Pyridoxal phosphate is the coenzyme of citrulline and the coenzyme of ornithine.
3. Pyridoxal phosphate is a drug used clinically to treat Parkinson's syndrome. Promote transaminase to carry out transamination and increase the content of dopamine in the body.