Pyridoxine(Vitamin b6)

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Vitamins

may regarded as organic compound required in our diet insmall amount to perform specific biological functions for

normal maintenance of optimum growth and health of the

organism

VITAMINS

WATER

SOLUBLE

NON B-COMPLEX

1.VITAMIN C

B COMPLEX

1.THIAMINE(B1)

2.RIBOFLAVIN(B2)

3.NIACIN(B3)

4.PYRIDOXINE(B6)

5.BIOTIN(B7)

6. PANTOTHENIC ACID(B5)

FAT

SOLUBLE

1.VITAMIN A

2.VITAMIN D

3.VITAMIN E

4.VITAMIN K


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PYRIDOXINE(VITAMIN B6)

Vitamin B6 is used to collectivelyrepresent the three compounds

namelya) Pyridoxine

b) Pyridoxal

c) pyridoxamine


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CHEMISTRY

Vitamin B6 compounds are Pyridinederivatives.

They differ from each other in structure of a

functional group attached to 4th

carbon in thepyridine ring.

PYRIDOXINE-Primary alcohol

PYRIDOXAL- aldehyde PYRIDOXAMINE-amine


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PYRIDOXINE-Primary alcohol

PYRIDOXAL- aldehyde

PYRIDOXAMINE-amine


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SYNTHESIS OF COENZYME

The active form of vitamin B6 is the coenzyme

PYRIDOXAL PHOSPHATE(PLP).

PLP can be synthesized by three compounds

pyridoxine, pyridoxal and pyridoxamine.

B6 is excreted in urine as 4-pyridoxic acid.


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ATP

ADP

KINASE

ATP

ADP

KINASE

-O-P

OO

4-Pyridoxic acidpyridoxine


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BIOCHEMICAL FUNCTIONS

PLP, the coenzyme of vitamin B6

is found attached to the -aminogroup of lysine in the enzyme.

PLP is closely associated with themetabolism of amino acids.

The synthesis of products such asserotonin, histamine, niacincoenzyme from the amino acids isdependent on pyridoxine.

Pyridoxal phosphate participatesin reactions like transamination,decarboxylation, deamination,transsulfuration, condensation

etc.


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TRANSAMINATION Pyridoxal phosphate is involved in the

transamination reaction (bytransaminase)converting amino acids to keto

acids.

DECARBOXYLATION Some of the -amino acids undergo

decarboxylation to form the respective amines.

This is carried out by a group of enzyme calleddecarboxylases which dependent on PLP.

Many biogenic amines with important function

are synthesized by PLP decarboxylation.


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a)SEROTONIN

Serotonin helps in nerve impulse transmission

(neurotransmitter).

It regulates sleep, behaviour, blood pressure etc.

tryptophan5-Hydroxytryptophan5-hydroxytryptamineco2

PLP


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b) catecholamine

Catecholamines are involved in metabolic and

nervous regulation.

TyrosineDOPAdopamine norepinephrine epinephrine

co2

PLP


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3.Pyridoxal phosphate is required for thesynthesis of-amino levulinic acid, the precursor

for heme synthesisGlycine

-amino--

Succinyl coA

4.PLP plays an important role in the metabolismof sulfur containing amino acids.

Transsulfuration (transfer of sulfur) fromhomocysteine to serine occurs in the synthesisof cysteine.

Levulinic

acid (ALA)

HemeALA synthase

PLP


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5. Deamination

Deamination of hydroxyl group containing

amino acid requires PLP.

SerineDehydratase

PLP

Pyruvate +NH3

ThreonineDehydratase

PLP- Ketobutyrate +NH3

6.SERINESerine is synthesized from glycine by a PLP

dependent enzyme hydroxymethyltransferase.

R d d di


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Recommended dietary

allowance(RDA)

The requirement of pyridoxine

for an adult is 2-2.2 mg/day .During pregnancy, lactation

and old age , an intake of

2.5mg/day is recommended.

DIETARY SOURCES

Animal sources such as eggyolk, fish , milk , meat are richin B6.

Vegetable sources wheat,corn, cabbage, roots and

tubers.


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Deficiency symptoms

It is associated with neurological symptomssuch as depression , irritability , nervousnes

and mental confusion.

Severe deficiency: The symptoms are related to synthesis of biogenic amines(serine, nor-

epinephrine and epinephrine). Demyelination ofneurons is also observed in vitamin B6 deficiency.

Pyridoxine antagonists: isoniazid,

deoxypridoxine and methoxy pyridoxine are

antagonists of B6.

Irritability

Nervousness Mentalconfusion

Depression


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THANK

YOU

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Pyridoxine(Vitamin b6)