Vitamin B6

Vitamin B₆ refers to a group of chemically very similar compounds which can be interconverted in biological systems. Vitamin B₆ is part of the vitamin B group, and its active form, pyridoxal 5'-phosphate (PLP) serves as a coenzyme in many enzyme reactions in amino acid, glucose, and lipid metabolism.

Forms

Several forms (vitamers) of vitamin B₆ are known:

All forms except pyridoxic acid and pyritinol can be interconverted. Absorbed pyridoxamine is converted to PMP by pyridoxal kinase, which is further converted to PLP by pyridoxamine-phosphate transaminase or pyridoxine 5’-phosphate oxidase which also catalyzes the conversion of PNP to PLP. Pyridoxine 5’-phosphate oxidase is dependent on flavin mononucleotide (FMN) as a cofactor which is produced from riboflavin (vitamin B₂) i.e. in this biochemical pathway, dietary vitamin B₆ cannot be used without vitamin B₂.