Vitamin B6

Question 0

Vitamin B6 exists as several vitamers, list 5.

Answer 0

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

Question 1

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

Answer 1

Pyridoxine (PN)

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

Question 2

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

Answer 2

Pyridoxine

Question 3

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

Answer 3

Pyridoxal

Question 4

Which vitamin B6 vitamer is the form in animal food?

Answer 4

Pyridoxamine

Question 5

Which vitamin B6 vitamer is generally considered the active form?

Answer 5

Pyridoxal-5-phosphate (PLP)

Question 6

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

Answer 6

Pyridoxine hydrochloride

Question 7

How is vitamin B6 absorbed and in what forms?

Answer 7

Passive diffusion, of non-phosphorylated forms:

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

Question 8

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

Answer 8

Animal sources

Question 9

How is vitamin B6 status assessed?

Answer 9

Direct measurement of vitamin B6 vitamers in blood or urine.

* most common is plasma PLP

Question 10

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

Answer 10

• Albumin

- Hemoglobin in RBCs

Question 11

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

Answer 11

Dephosphorylation

Question 12

What is the primary metabolic site for vitamin B6 metabolism?

Answer 12

Liver

Question 13

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

Answer 13

PLkinase (Pyridoxal kinase)

Question 14

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

Answer 14

Adenosine triphosphate-zinc

Question 15

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

Answer 15

• Riboflavin status
• Niacin status
• Zinc status

Question 16

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

Answer 16

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

Question 17

What is the most common vitamin B6 coenzyme form?

Answer 17

Pyridoxal-5-phosphate (PLP)

Question 18

In homocysteine metabolism, both enzymes are?

Homocysteine -> Cystathionine -> Cysteine

Answer 18

Cystathionine synthase & Cystathionine lyase

* PLP-dependent

Question 19

Ultimately, need for vitamin B6 depends on what?

Answer 19

Protein intake

Question 20

_______ vitamin B6 per 1 g protein

Answer 20

0.016 mg

Question 21

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

Answer 21

PL & PM

Question 22

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

Answer 22

PN - pyridoxine

Question 23

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

Answer 23

PN - pyridoxine

Question 24

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

Answer 24

- Anticonvulsants - Corticosteroids - Penicillamine

Question 25

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

Answer 25

- Parkinson's disease pts. on L-dopa - Newborns or other pts. with convulsions and seizures - Alcoholics

Question 26

Pyridoxine deficiency is _____ in the US under normal conditions.

Answer 26

Rare

Question 27

How long does a Pyridoxine deficiency take to develop symptoms?

Answer 27

Takes about 2 months

Question 28

Name 3 pyridoxine deficiency symptoms?

Answer 28

Poor appetite, weakness, sleeplessness

Question 29

What does pyridoxine deficiency cause due to impaired heme synthesis?

Answer 29

- Microcytic hypochromic anemia

Question 30

What are the signs of pyridoxine toxicity?

Answer 30

Signs are similar to deficiency

Question 31

What is the main symptom of pyridoxine toxicity?

Answer 31

Neurological symptoms

Question 32

What does pyridoxine deficiency cause due to impaired serotonin synthesis?

Answer 32

Central and peripheral nervous system disorders

Question 33

What does pyridoxine deficiency cause especially in pregnant women?

Answer 33

- Glucose intolerance

Question 34

What dermatological problems are caused by pyridoxine deficiency?

Answer 34

- Glossitis & Stomatitis

Question 35

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

Answer 35

- Retarded growth, reproductive capacity

Question 36

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

Answer 36

- Hyperhomocysteinemia