Vitamin B6 (Pyridoxine)
- Vitamin B1 (Thiamine) Biochemistry
- Vitamin B1 (Thiamine) Deficiency
- Vitamin B2 (Riboflavin)
- Vitamin B3 (Niacin) Biochemistry
- Vitamin B3 (Niacin) Deficiency and Excess
- Hartnup Disease
- Vitamin B5 (Pantothenic Acid)
- Vitamin B6 (Pyridoxine)
- Vitamin B7 (Biotin)
- Vitamin B9 (Folate)
- Vitamin B12 (Cobalamin) Biochemistry
- Vitamins B9 and B12 Deficiencies
- Vitamin A (Retinol) Biochemistry
- Vitamin A (Retinol) Deficiency and Excess
- Vitamin C (Ascorbic Acid) Biochemistry
- Vitamin C (Ascorbic Acid) Deficiency and Excess
- Vitamin D Biochemistry
- Vitamin D Deficiency and Excess
- Vitamin E (Tocopherol/Tocotrienol)
- Vitamin K Biochemistry
- Vitamin K Deficiency
- Zinc
- Kwashiorkor and Marasmus
Summary
Vitamin B6 (Pyridoxine) refers to a group of water-soluble vitamins important in metabolic reactions via its active form, PLP (pyridoxal 5′-phosphate). PLP is involved in a number of enzymatic reactions, including transamination, decarboxylation, that of glycogen phosphorylase. PLP is also involved in neurotransmitter synthesis, cystathionine synthesis, histamine synthesis, heme synthesis, and gene expression.
Given its important physiologic roles, Vitamin B6 deficiency can present with many signs and symptoms. Examples include neuropathy (paresthesias), convulsions and a sideroblastic anemia secondary to ALA synthase dysfunction. Vitamin B6 deficiency can be caused by a variety of reasons, but classically is seen in the setting of oral contraceptive or isoniazid use.
Key Points
- Vitamin B6 (Pyridoxine)
- Active form is pyridoxal phosphate (PLP), a cofactor for various reactions:
- transamination (eg. ALT in Pyruvate Metabolism)
- decarboxylation (eg. DOPA decarboxylase in Catecholamine Synthesis)
- glycogen phosphorylase
- used to treat McArdle’s disease (Type 5 GSD)
- Important in synthesis of:
- Cystathionine
- via cystathionine synthase (in Homocysteine Metabolism)
- Heme
- via ALA synthase (in Heme Synthesis)
- Niacin (Vitamin B3)
- Histamine and most neurotransmitters (serotonin, epinephrine, norepinephrine, dopamine, GABA)
- Cystathionine
- Active form is pyridoxal phosphate (PLP), a cofactor for various reactions:
- Vitamin B6 Deficiency
- most common in patients taking isoniazid/INH (for TB) or oral contraceptives
- Isoniazid inhibits pyridoxine phosphokinase, which converts pyridoxine to PLP (active form)
- Due to its many functions, deficiency presents with many symptoms, including:
- Peripheral neuropathy
- Sideroblastic anemias
- due to role as cofactor for ALA synthase
- presents as microcytic, hypochromic anemia
- Convulsions/seizures, hyperirritability, seborrheic dermatitis, glossitis also seen (nonspecific, low-yield)
- most common in patients taking isoniazid/INH (for TB) or oral contraceptives
Find Vitamin B6 and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.