Chemistry of vitamin B1, Biochemical functions of vitamin B1, Recommended dietary Allowance of Thiamine, Dietary sources of Thiamine ,Deficiency symptoms of Thiamine

1. Chemistry and Biochemical role,
RDA and Deficiency diseases of
Vitamin B1
Jasmine Juliet .R
Biotechnology Department
Agricultural college and
Research & Institute
Madurai.

2. Thiamine (Vitamin B1) - Introduction
Thiamine (anti-beri beri or antinuritic vitamin)
is water soluble.
 It has a specific coenzyme, Thiamine
pyrophosphate (TPP or cocarboxylase) which
is mostly associated with carbohydrate
metabolism.

4. Thiamine (Vitamin B1) - Chemistry
 Thiamine is soluble in water and easily destroyed by heat or
oxidation especially in the presence of baking soda.
 The term Thiamine indicates that it is a sulphur- and nitrogen-
containing substance.
 Thiamine contains a pyrimidine ring and a thiazole ring held
by a methylene bridge.

5. Thiamine (Vitamin B1) - Chemistry
 Thiamine is the only natural compound with thiazole
ring.
 The alcohol (OH) group of thiamine is esterified with
phosphate (2 moles) to form the coenzyme, Thiamine
pyrophosphate (TPP or cocarboxylase).
 The pyrophsphate moiety is donated by ATP and the
reaction is catalysed by the enzyme thiamine
pyrophosphate transferase.

8. Thiamine (Vitamin B1) - Biochemical
functions
(I) The coenzyme, Thiamine pyrophosphate or cocarboxylase
is intimately connected with the energy releasing reactions in
the carbohydrate metabolism.
(II) The enzyme Pyruvate dehydrogenase catalyses ( Oxidative
decarboxylation) the irreversible conversion of pyruvate to
acetyl CoA.
 This reaction is dependent on TPP, besides the other
coenzymes.

9. Thiamine (Vitamin B1) – Biochemical
functions
(III) α - Ketoglutarate dehydrogenase is an enzyme of
the citric acid cycle.
 This enzyme is comparable with pyruvate
dehydrogenase and requires TPP.
(IV) Transketolase of the hexose monophosphate shunt
is dependent on TPP.

10. Thiamine (Vitamin B1) – Biochemical
Functions
(V) The branched chain α - Keto acid
dehydrogenase (decarboxylase) catalyses the
oxidative decarboxylation of branched chain
aminoacids (Valine, Leucine, and isoleucine) to
the respective keto acids.
This enzyme also requires TPP.

11. Thiamine (Vitamin B1) – Biochemical
Functions
(VI) TPP plays an important role in the
transmission of nerve impulse.
It is believed that TPP is required for
acetylcholine sythesis and the ion
translocation of neural tissue.

12. Thiamine (Vitamin B1) – Biochemical
Functions
 (VII) Thiamine plays a role in the conversion of the
aminoacid tyrptophan to Niacin.
 (VIII) Thiamine has several indirect functions in the
body because of its role in energy metabolism like:
 Maintenance of appetite.
 Maintenance of muscle tone
 Maintenance of healthy mental attitude.

16. Thiamine (Vitamin B1) - Recommended
dieary allowance (RDA)
The daily requirement of thiamine depends on
the intake of carbohydrate.
 A dietary supply of 1-1.5mg/day is
recommended for adults (about
0.5mg/1000cals of energy).

18. Thiamine (Vitamin B1) – Dietary
Sources
Cereals, pulses, oil seeds, nuts and yeast are
good sources.
Polishing of rice removes about 80% of
Thiamine.
Vitamin B1 is also present in animal foods
like pork, liver, heart, kidney, milk, etc.

21. Thiamine (Vitamin B1) – Deficiency
Symptoms
The deficiency of vitamin B1 results in a
condition called Beri-Beri.
Beri-Beri is mostly seen in populations
consuming exclusively polished rice as staple
food.

22. Thiamine (Vitamin B1) – Deficiency
Symptoms
The early symptoms of Thiamine deficiency are:
 Loss of appetite (anorexia), Weakness,
Constipation, Nausea,
 Mental depression, Peripheral neuropathy, Irritability,
etc.
Numbness in the legs complaints of ‘pins and
needles sensations’ are reported.