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Metabolism II > Vitamin B6 > Flashcards

Vitamin B6 Flashcards

0
Q

Vitamin B6 exists as several vitamers, list 5.

A
  1. Pyridoxine
  2. Pyridoxal
  3. Pyridoxamine
  4. Pyridoxal-5-phosphate (PLP)
  5. Pyriodoxine hydrochloride
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1
Q

Vitamin B6 was first reported in 1934 as…, followed by…

A

Pyridoxine (PN)

Followed by: Pyridoxal (PL) & Pyridoxamine (PM)

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2
Q

Which vitamin B6 vitamer is the form in vegetables and has low bioavailability?

A

Pyridoxine

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3
Q

Which vitamin B6 vitamer is the form in animal food that is unstable and destroyed by cooking?

A

Pyridoxal

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4
Q

Which vitamin B6 vitamer is the form in animal food?

A

Pyridoxamine

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5
Q

Which vitamin B6 vitamer is generally considered the active form?

A

Pyridoxal-5-phosphate (PLP)

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6
Q

Which vitamin B6 vitamer is the synthetic form of vitamin B6?

A

Pyridoxine hydrochloride

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7
Q

How is vitamin B6 absorbed and in what forms?

A

Passive diffusion, of non-phosphorylated forms:

  • Pyridoxine (PN)
  • Pyridoxal (PL)
  • Pyridoxamine (PM)
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8
Q

Vitamin B6 is slightly better absorbed when it is from what source?

A

Animal sources

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9
Q

How is vitamin B6 status assessed?

A

Direct measurement of vitamin B6 vitamers in blood or urine.

* most common is plasma PLP

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10
Q

In the bloodstream what is vitamin B6 bound to for transport? (2)

A
  • Albumin

- Hemoglobin in RBCs

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11
Q

What is required before vitamin B6 can be uptaken from the circulation into tissues?

A

Dephosphorylation

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12
Q

What is the primary metabolic site for vitamin B6 metabolism?

A

Liver

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13
Q

What enzyme is responsible for the phosphorylation of PN, PL & PM to PNP, PLP, & PMP, respectively?

A

PLkinase (Pyridoxal kinase)

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14
Q

Pyridoxal kinase uses what co-substrate for the phosphorylation of PN, PL, & PM?

A

Adenosine triphosphate-zinc

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15
Q

The metabolism (intraconverting between 6 vitamers) of vitamin B6 depends on what 3 statuses?

A
  • Riboflavin status
  • Niacin status
  • Zinc status
16
Q

What is vitamin B6 responsible for the metabolism of? (6)

A
  • Amino acids (involved in approx 60 reactions with amino acids)
  • One-carbon units (methyl groups)
  • Lipids
  • Gluconeogenesis pathways
  • Heme synthesis
  • Neurotransmitter biosynthesis (Dopamine & Norepinephrine)
17
Q

What is the most common vitamin B6 coenzyme form?

A

Pyridoxal-5-phosphate (PLP)

18
Q

In homocysteine metabolism, both enzymes are?

Homocysteine -> Cystathionine -> Cysteine

A

Cystathionine synthase & Cystathionine lyase

* PLP-dependent

19
Q

Ultimately, need for vitamin B6 depends on what?

A

Protein intake

20
Q

_______ vitamin B6 per 1 g protein

A

0.016 mg

21
Q

Vitamin B6 in meat, fish, eggs, & dairy products is found in what form?

A

PL & PM

22
Q

Vitamin B6 in plants, vegetables, & whole-grain cereals is found in what form?

A

PN - pyridoxine

23
Q

What vitamin B6 vitamer is easily destroyed by processing, canning, heating, freezing an milling?

A

PN - pyridoxine

24
Q

Name 3 of the many drugs that interfere with B6 metabolism, putting people at risk for a deficiency.

A
  • Anticonvulsants
  • Corticosteroids
  • Penicillamine
25
Q

The beneficial effects of B6 supplementation have been seen in who? (3)

A
  • Parkinson’s disease pts. on L-dopa
  • Newborns or other pts. with convulsions and seizures
  • Alcoholics
26
Q

Pyridoxine deficiency is _____ in the US under normal conditions.

A

Rare

27
Q

How long does a Pyridoxine deficiency take to develop symptoms?

A

Takes about 2 months

28
Q

Name 3 pyridoxine deficiency symptoms?

A

Poor appetite, weakness, sleeplessness

29
Q

What does pyridoxine deficiency cause due to impaired heme synthesis?

A
  • Microcytic hypochromic anemia
30
Q

What are the signs of pyridoxine toxicity?

A

Signs are similar to deficiency

31
Q

What is the main symptom of pyridoxine toxicity?

A

Neurological symptoms

32
Q

What does pyridoxine deficiency cause due to impaired serotonin synthesis?

A

Central and peripheral nervous system disorders

33
Q

What does pyridoxine deficiency cause especially in pregnant women?

A
  • Glucose intolerance
34
Q

What dermatological problems are caused by pyridoxine deficiency?

A
  • Glossitis & Stomatitis
35
Q

What is caused by pyridoxine deficiency (b/c of amino acid metabolism)

A
  • Retarded growth, reproductive capacity
36
Q

What condition of the blood is a result of pyridoxine deficiency?

A
  • Hyperhomocysteinemia

Metabolism II (7 decks)

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