Vitamins B5 and B6

Question 1

Vitamin B6 comprises six chemically related compounds namely …. The most active of these compounds is ________.

Answer 1

pyridoxine, pyridoxamine, pyridoxal, [and their respective phosphorylated derivatives] pyridoxine 5-phosphate, pydridoxamine 5-phosphate, pyridoxal-5-phosphate
The most active of these is pyridoxal 5-phosphate.

Question 2

sources of Vitamin B6

Answer 2

beef, pork, fish, eggs etc.

Question 3

role of pyridoxine

Answer 3

1. It is required in the transamination reactions of amino acids. [Transamination is a biochemical process that involves the transfer of an amino group from one amino acid to a keto acid, producing a new amino acid and a corresponding new keto acid.]
2. It is a coenzyme of cystathionine synthase and cystathionase, enzymes that catalyze reactions in the catabolism of methionine.
3. It is required for the conversion of Tryptophan to Niacin (Vitamin B3).
4. It is required in the synthesis of neurotransmitters: serotonin, dopamine, epinephrine, norepinephrine, and gamma-aminobutyric acid (GABA).
5. It is a coenzyme of glycogen phosphorylase hence is important in glycogenolysis.
6. It is required in sphingolipid synthesis required for myelin formation.
7. It is required in synthesis of haemoglobin.

Question 4

deficiency complications of Vitamin B6

Answer 4

• neuropathy; due to impaired sphingolipid synthesis
• microcytic anaemia [smaller than usual RBCs]; due to impaired heme synthesis

Question 5

1. Vitamin B5 (aka. ____(a)____ acid) is a component of ____(b)____, a coenzyme that serves as an acyl group carrier in certain enzymatic reactions.
2. What are symptoms of deficiency of Vitamin B5?

Answer 5

1. (a) pantothenic, (b) coenzyme A
2. Apathy, depression, impaired adrenal function and muscular weakness.

Question 6

State the components of coenzyme A.

Answer 6

• β-mercaptoethylamine
• pantothenic acid
• 3’-phosphoadenosine diphosphate (3’-P-ADP)
• ribose