Vitamin B6 - Pyrodoxine

Question 1

What are the different forms of B6?

Answer 1

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

Question 2

What are the coenzyme forms of B6?

Answer 2

(PLP) pyridoxal 5’ phosphate (most active!)
(PMP) pyridoxamine 5’-phosphate
(PNP) pyridoxine 5’-phosphate

Question 3

What is the function of PLP?

Answer 3

essential for protein metabolism
PLP is the most active form of B6 (pyrodoxine)

PLP is a coenzyme for ~160 enzymatic reactions including the following:

• transamination (aminotransferases)
• decarboxylation (DOPA decarboxylase)
• dehydration (serine dehydratase)
• gluconeogenesis & glyconeolysis
• transsulfuration (catabolism of homocysteine, cysteine synthesis)

PLP coenzyme function in many aspects of AA metabolism, also involved in gluconeogenesis and glycogenolysis, neurotransmitter metabolism (DOPA –> dopamine, serotonin synthesis)

Question 4

How and why can vitamin B6 deficiency increases homocysteine levels?

Answer 4

Homocysteine = intermediate in the metabolism of methionine
Two PLP-dependent enzymes are required to convert homocysteine to the AA cysteine in the homocysteine transsulfuration pathway.
If the PLP-dependent enzymes are unable to have adequate PLP (through the dietary intake of B6) the conversion of homocysteine to cysteine will not be able to occur, resulting in an accumulation of homocysteine when there is a B6 deficiency present

Question 5

What are the three vitamins that may influence the status of homocysteine in the blood?

Answer 5

Folate (B9)
Vitamin B12
Vitamin B6 (pyridoxine)

Question 6

How can B6 deficiency lead to anemia?

What type of anemia is caused by B6 deficiency?

Answer 6

microcytic anemia occurs during vitamin B6 deficiency

microcytic anemia = the body’s tissues/organs do not get enough oxygen due to a deficiency in RBCs, OR the RBCs do not have enough hemoglobin (the protein that transports oxygen in the blood)

Anemia can occur because pyridoxine is needed for iron to convert to hemoglobin, otherwise, it will remain as heme. (deficiency in pyridoxine results in normal to high iron levels because of the inhibited/limited conversion of heme to hemoglobin)

Question 7

What are the natural dietary sources of B6 (pyridoxine)?

Answer 7

fish
yeast
meat
egg yolk
cereals
grains
vegetables
fruits

Question 8

What are artificial sources of B6 (Pyridoxine)?

Answer 8

enriched foods

vitamin B complex supplements

Question 9

What are the primary functions of B6?

Answer 9

transaminases –> transamination (protein) reactions
phosphorylase (glycogen) –> glycogen metabolism (muscle)
decarboxylase –> decarboxylation (remove CO2)

Question 10

What is the unique amino group found in the structure of B6 (pyridoxine)?

Answer 10

NH2