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Pyridoxal 5'-Phosphate (PLP)

Active coenzyme form of vitamin B6 that participates in over 150 enzymatic reactions, predominantly transaminations, decarboxylations, and one-carbon transfers in amino acid and neurotransmitter metabolism.

Also: P5P, PLP

PLP is the cofactor for AST and ALT (transamination), cystathionine β-synthase (transsulfuration of homocysteine), GAD (GABA synthesis), AADC (dopamine/serotonin synthesis), and ALAS (heme synthesis). Plasma PLP <20 nmol/L indicates deficiency. PLP is depressed by inflammation (acute-phase response), oral contraceptives, and isoniazid. Vitamin B6 excess (chronic >100 mg/d) causes sensory peripheral neuropathy, the basis of the UL.

How one textbook covers it

  • Modern Nutrition in Health and Disease, 12th ed. — Ch 27: Vitamin B6

    PLP is the cofactor for AST and ALT (transamination), cystathionine β-synthase (transsulfuration of homocysteine), GAD (GABA synthesis), AADC (dopamine/serotonin synthesis), and ALAS (heme synthesis). Plasma PLP <20 nmol/L indicates deficiency. PLP is depressed by inflammation (acute-phase response), oral contraceptives, and isoniazid. Vitamin B6 excess (chronic >100 mg/d) causes sensory peripheral neuropathy, the basis of the UL.

Related terms

GABA, Heme, Homocysteine, Vitamin B6