Vitamin B6 (Pyridoxine)
(Rat anti dermatitis factor)
Introduction
In 1934 Györgyi observed that an extract of yeast
cured dermatitis in rats which was not curable with other members of B vitamins
and isolated from natural sources in 1938. Stiller and others characterised its
structure in 1939. It is a pyridine derivative which was synthesized in 1999 by
Harris et al and by Kuhn and others.
Chemistry
Two allied compounds of pyridoxine, pyridoxal (natural)
and pyridexamine (synthetic) have the same action.
All the three varieties are known as vitamin B5.
Pyridoxal phosphate is the active form.
Properties
·
white, crystal
·
soluble in water
·
heat stable in both acidic and alkaline
solutions
Distribution
Animal
sources
·
Liver
·
egg yolk
·
meat
·
milk
Vegetable
sources
·
Germs of various grains
·
seeds
·
leafy vegetables
·
yeast
Functions
(1) To takes part in normal
tryptophan metabolism.
(2) Pyridoxal phosphate also acts
as co enzyme for the some enzymes like transaminase or amino transferase,
Decarboxylases, deaminase etc.
(3) Pyridoxal phosphate is related
to the formation of long chain polyunsaturated fatty acids.
(4) Helps in the synthesis of fats
from proteins and carbohydrates.
(5) It plays part in the inter
conversion of serine and glycine in presence of tetrahydrofolic acid also.
(6) Helps in transulphurase and
thionase reactions converting homocysteine and cystathionine to cysteine.
(7) The coenzyme is required in the
synthesis of δ-amino levulinic acid-an intermediate in porphyrin synthesis.
(8) Pyridoxal phosphate is an essential
component of phosphorylase.
Deficiency
signs
·
Peculiar dermatitis (acrodynia)
·
reduced growth
·
degeneration of the nerves
·
reproductive failure
·
hypochromic microcytic anaemia
·
weakness of muscles
·
convulsive seizures
Daily
requirement
In infants 0.3 mg and in adults 2 mg per day,
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