Thiamine (vitamin B1) is a water-soluble vitamin that acts as a cofactor for several enzyme complexes involved in carbohydrate metabolism. It contains pyrimidine and thiazole rings joined by a methylene bridge. Thiamine is converted to its active coenzyme form, thiamine pyrophosphate (TPP), which participates in reactions like glycolysis and the citric acid cycle. Deficiency can result in beriberi disease, characterized by neuropathy or heart failure depending on whether the dry or wet form occurs. Diagnosis involves measuring transketolase levels in red blood cells.

1. THIAMINE (B1]
Shyam sundar yadav
Nims college of paramedical

2. THIAMINE B1
 Thiamine (anti-beri-beri or antineuritic vitamin) is
water soluble vitamin
o It has a specific coenzyme, thiamine
pyrophosphate (TPP)
o Chemistry:
o Thiamine contains pyrimidine ring and a thiazole
ring held by a methylene bridge

3.  The alcohol group of thiamine is esterfied with
phosphate (2 moles) to form the coenzyme,
thiamine pyrophosphate
(TPP or Cocarboxylase)
 The phosphate moiety is donated by ATP &
reaction is catalyzed by thiamine pyrophosphate
transferase
 Thiamine is a sulphur containing water soluble
vitamin

4. N
N
NH2
H3C
CH2
S
N
O O
-CH2 - CH2 – O - P- O – P - O
O O
Pyrimidine ring
Methylene bridge
Thiazole Pyrophosphate
CH3
Structure of
TPP

5.  Metabolism:
 Absorption: Thiamin is carried by the portal blood
to the liver, present as free thiamine
 Storage: stored as thiamin pyrophosphate
 Mainly stored in skeletal muscle and also
present in significant amounts in liver, heart,
kidneys, erythrocytes and nervous system
 Coenzyme form: TPP

6.  The coenzyme, TPP or Cocarboxylase is
connected with energy releasing reactions in the
carbohydrate metabolism
Pyruvate dehydrogenase complex:
 It catalyses the irreversible conversion of pyruvate
to acetyl CoA
 It is essential for complete oxidation of glucose
 It links glycolysis and TCA cycle

7. Acetyl CoA
 Transketolase is dependent on TPP
 It is involved in HMP shunt
Pyruvate
PDH Complex
TPP
NAD+
NADH + H+

8.  α- Ketoglutarate dehydrogenase
complex:
 It converts α- Ketoglutarate succinyl CoAin
TCA cycle
α-Ketoglutarate
Succinyl CoA
α- Ketoglutarate DH Complex
TPP
NAD+
NADH + H+

9. Corresponding Acyl CoA
 Essential for transmission of nerve impulse
 TPP is required for synthesis of Acetylcholine
NADH + H+
 The branched chain α-Keto acid
dehydrogenase (decarboxylase):
 It catalyses the conversion of α-keto acids to
corresponding acyl CoA
Branched chain α-Keto acid
NAD+
Branched chain α-Keto acid DH Complex
TPP

10. Glucose Glucose – 6 P
Pyruvate
Acetyl CoA
TPP PDH
TCA
TPP
Succinyl CoA
Citrate
Oxaloacetate
α- Ketoglutarate
α- Ketoglutarate
dehydrogenase
Ribose - 5P
Transketolase
TPP
Seduheptulose - 7P
Xylulose - 5P
Glyceraldehyde - 3P

11.  Rich sources of thiamine are unrefined cereal
grains (rice, wheat), legumes (beans)
 Animal sources are liver, kidney, milk
 Thiamine is mostly concentrated in outer layer of
cereals
 Polishing of rice removes 80% of thiamine
 Thiamine is water soluble, and is excreted into
water during cooking process

12.  Adults - 1-1.5 mg/day
 Children - 0.7-1.2 mg/day
 Pregnancy & lactation
Deficiency :
Causes:
- 2 mg/day
B1 deficiency is caused by inadequate
intake of thiamine in diet

13.  Eating fishes containing microbial thiaminase, it
hydrolytically destroys thiamin
 Impaired absorption is caused by intestinal
diaorders
 Increased requirement of thiamine is seen in
hyperthyroidism, fever, pregnancy and lactation
 Chronic alcoholism is common cause of B1
deficiency

14. BIOCHEMICAL CHANGES IN B1 DEFICIENCY
 Carbohydrate metabolism is impaired
 Accumulation of pyruvate in tissues
 Excretion of pyruvate in urine
 Normally, pyruvate does not cross the blood-brain
barrier (BBB)
 In thiamine deficiency alteration occurs in BBB and
permits pyruvate into brain
 It results in disturbed metabolism, it may be
responsible for polyneuritis

15.  B1 deficiency leads to impairment in nerve impulse
transmission due to lack of TPP
 Transketolase activity in erythrocytes is decreased
 Measurement of RBC transketolase activity is
reliable diagnostic test to assess B1 deficiency

16.  Thiamine deficiency causes a clinical condition
called Beri-Beri
 Commonly seen in populations consuming
exclusively polished rice as staple food
 Clinical features of thiamine deficiency are
grouped into
 Wet beri-beri:
 It is characterized by edema of legs, face, trunk &
serous cavities

17.  Systolic BP is elevated & diastolic BP is decreased
 Tachycardia
 Fast & bouncing pulse is observed
 Enlargement of heart
 Heart becomes weak & death may occur due to
heart failure

19.  Dry beri-beri:
 Associated with neurological manifestations
 Clinical features
 Peripheral neuritis with numbness
 Tingling sensations in the lower legs & feet
 Ataxic gait
 Loss of weight
 Muscles become weak & walking becomes difficult
 Mental confusion

20.  Called as Wernicke-Korsakoff syndrome
 Mostly seen in chronic alcoholics
 Insufficient intake or impaired absorption of
thiamine
 Loss of memory,
 Apathy
 Rhythmical to & fro motion of eye balls

21.  Seen in infants born to mothers suffering from
thiamine deficiency
 The breast milk of these mothers contain low
levels of thiamine
 It usually occurs during 2-4 months
 Clinical features include
 Sleeplessness
 Restlessness
 Vomiting, convulsions
 Death may occur due to cardiac failure

22.  Increased plasma levels of pyruvate & lactate due
to low activity of PDH complex
 Accumilation of pentose sugars in erythrocytes is
due to decreased activity of transketolase
 Measurement of Transketolase activity is common
test used for the diagnosis of B1 deficiency

23.  Antimetabolites
 Thiaminase
 It is present in raw fish & seafood
 Thiaminase destroys thiamine if it is present
in the diet

24. REFERENCES
 Harper’s Biochemistry 25th Edition.
 Fundamentals of Clinical Chemistry by Tietz.
 Text Book of Medical Biochemistry-A R Aroor.
 Text Book of Biochemistry-DM Vasudevan
 Text Book of Biochemistry-MN Chatterjea
 Text Book of Biochemistry-Dr.U.Satyanarana