Vitamin B6 Flashcards
Vitamin B6 exists as several vitamers, list 5.
- Pyridoxine
- Pyridoxal
- Pyridoxamine
- Pyridoxal-5-phosphate (PLP)
- Pyriodoxine hydrochloride
Vitamin B6 was first reported in 1934 as…, followed by…
Pyridoxine (PN)
Followed by: Pyridoxal (PL) & Pyridoxamine (PM)
Which vitamin B6 vitamer is the form in vegetables and has low bioavailability?
Pyridoxine
Which vitamin B6 vitamer is the form in animal food that is unstable and destroyed by cooking?
Pyridoxal
Which vitamin B6 vitamer is the form in animal food?
Pyridoxamine
Which vitamin B6 vitamer is generally considered the active form?
Pyridoxal-5-phosphate (PLP)
Which vitamin B6 vitamer is the synthetic form of vitamin B6?
Pyridoxine hydrochloride
How is vitamin B6 absorbed and in what forms?
Passive diffusion, of non-phosphorylated forms:
- Pyridoxine (PN)
- Pyridoxal (PL)
- Pyridoxamine (PM)
Vitamin B6 is slightly better absorbed when it is from what source?
Animal sources
How is vitamin B6 status assessed?
Direct measurement of vitamin B6 vitamers in blood or urine.
* most common is plasma PLP
In the bloodstream what is vitamin B6 bound to for transport? (2)
- Albumin
- Hemoglobin in RBCs
What is required before vitamin B6 can be uptaken from the circulation into tissues?
Dephosphorylation
What is the primary metabolic site for vitamin B6 metabolism?
Liver
What enzyme is responsible for the phosphorylation of PN, PL & PM to PNP, PLP, & PMP, respectively?
PLkinase (Pyridoxal kinase)
Pyridoxal kinase uses what co-substrate for the phosphorylation of PN, PL, & PM?
Adenosine triphosphate-zinc
The metabolism (intraconverting between 6 vitamers) of vitamin B6 depends on what 3 statuses?
- Riboflavin status
- Niacin status
- Zinc status
What is vitamin B6 responsible for the metabolism of? (6)
- Amino acids (involved in approx 60 reactions with amino acids)
- One-carbon units (methyl groups)
- Lipids
- Gluconeogenesis pathways
- Heme synthesis
- Neurotransmitter biosynthesis (Dopamine & Norepinephrine)
What is the most common vitamin B6 coenzyme form?
Pyridoxal-5-phosphate (PLP)
In homocysteine metabolism, both enzymes are?
Homocysteine -> Cystathionine -> Cysteine
Cystathionine synthase & Cystathionine lyase
* PLP-dependent
Ultimately, need for vitamin B6 depends on what?
Protein intake
_______ vitamin B6 per 1 g protein
0.016 mg
Vitamin B6 in meat, fish, eggs, & dairy products is found in what form?
PL & PM
Vitamin B6 in plants, vegetables, & whole-grain cereals is found in what form?
PN - pyridoxine
What vitamin B6 vitamer is easily destroyed by processing, canning, heating, freezing an milling?
PN - pyridoxine
Name 3 of the many drugs that interfere with B6 metabolism, putting people at risk for a deficiency.
- Anticonvulsants
- Corticosteroids
- Penicillamine
The beneficial effects of B6 supplementation have been seen in who? (3)
- Parkinson’s disease pts. on L-dopa
- Newborns or other pts. with convulsions and seizures
- Alcoholics
Pyridoxine deficiency is _____ in the US under normal conditions.
Rare
How long does a Pyridoxine deficiency take to develop symptoms?
Takes about 2 months
Name 3 pyridoxine deficiency symptoms?
Poor appetite, weakness, sleeplessness
What does pyridoxine deficiency cause due to impaired heme synthesis?
- Microcytic hypochromic anemia
What are the signs of pyridoxine toxicity?
Signs are similar to deficiency
What is the main symptom of pyridoxine toxicity?
Neurological symptoms
What does pyridoxine deficiency cause due to impaired serotonin synthesis?
Central and peripheral nervous system disorders
What does pyridoxine deficiency cause especially in pregnant women?
- Glucose intolerance
What dermatological problems are caused by pyridoxine deficiency?
- Glossitis & Stomatitis
What is caused by pyridoxine deficiency (b/c of amino acid metabolism)
- Retarded growth, reproductive capacity
What condition of the blood is a result of pyridoxine deficiency?
- Hyperhomocysteinemia
