Thiamine (vitamin b1) and riboflavin (vitamin b2) actions as co-enzyme

1. THIAMINE (VITAMIN B 1 ) RIBOFLAVIN (VITAMIN B 2 ) Maryam Jamilah Binti Abdul Hamid 082013100002 IMS Bangalore

2. Learning outcome Student should be able to know the activity of both vitamins as coenzyme Student should be able to list down the effect of deficiency in both vitamins.

3. INTRODUCTION Thiamine Source: Aleurone layer of cereals Daily requirement: 1-1.5 mg/day Riboflavin Source: liver,dried yeast,egg,whole milk, fish , cereals,legumes & green leafy vegetables Daily requirement: 1.5 mg/day. Pregnant lady, lactation & old age need additional 0.2-0.4 mg/day

4. THIAMINE (VITAMIN B 1 ) Pyruvate dehydrogenase Coenzyme form: Thiamine pyrophosphate (TPP) Process: oxidative decarboxylation of alpha keto acids Pyruvate Acetyl CoA + CO 2 Pyruvate dehydrogenase TPP

5. Alpha ketoglutarate dehydrogenase Coenzyme form: Thiamine pyrophosphate (TPP) Process: oxidative decarboxylation of alpha ketoglutarate Alpha ketoglutarate Succinyl CoA + CO 2 Alpha ketoglutarate dehydrogenase TPP

6. Transketolase Coenzyme form: Thiamine pyrophosphate (TPP) Process: HMP shunt Ribulose-5-phosphate Glyceraldehyde-3-phosphate Xylulose-5-phosphate Sedoheptulose-7-phosphate Transketolase TPP

7. Deficiency Manifestations of Thiamine Beriberi Early symptoms: Anorexia Dyspepsia Heaviness Weakness Easily exhausted Wet Beriberi Cardiovascular manifestation Edema L eg Face Trunk Serous cavities Palpitation Breathlessness Distended neck veins

8. Dry Beriberi Central Nervous System (CNS) manifestation Difficulty in walking Peripheral neuritis with sensory disturbance Complete paralysis Infantile Beriberi Mother is thiamine deficiency Restlessness Sleeplessness

9. Wernicke-Korsakoff Syndrome / Cerebral beriberi Encelopathy (malfunction of the brain) Ophthalmoplegia Nystagmus Cerebellar ataxia Psychosis Polyneuritis Alcohol inhibits intestinal absorption of thiamine Impairment of conversion of pyruvate to acetyl CoA Increased plasma con. p yruvate and lactate Lactic acidosis Pregnancy Old age

10. RIBOFLAVIN (VITAMIN B 2 ) 2 types of coenzyme :- Flavin mono nucleotide (FMN) Flavin adenine dinucleotide (FAD) Enzymes containing riboflavin are called flavoprotein

11. FMN-dependent enzyme Amino acid oxidation FMN is reduced Reoxidised by molecular O 2 to produce H 2 O 2 L-amino acid L- imino acid FMN FMNH 2 H 2 0 + 1/2O 2 H 2 O 2 O 2 Catalase

12. Respiratory chain Complex I NADH dehydrogenase complex contain FMN e - are transported in the following manner NAD + FMN CoQ FMN collect e - from NADH and pass to Fe-S NADH + H + + FMN FMNH 2 + NAD +

13. FAD Accepts Hydrogen FAD accepts 2H + and 2e - FAD + 2H + FADH 2 FAD is reduced.

14. FAD-dependent enzyme Succinate fumarate FAD FADH2 Acyl CoA α - β - unsaturated acyl CoA FAD FADH2 succcinate dehydrogenase acyl CoA dehydrogenase CITRIC ACID CYCLE BETA OXIDATION

15. FAD-dependent enzyme (cont.) DEGRADATION OF PURINE NUCLEOTIDE

16. Riboflavin Deficiency Uncommon because riboflavin is synthesized by the intestinal flora but it is possible ! Usually accompanies other deficiency diseases:- Beriberi (deficiency of thiamine) Pellagra (deficiency of niacin) Kwashiorkor (protein-energy malnutrition)

17. Manifestations for Riboflavin Glossitis inflammation with depapillation of the dorsal surface of the tongue Magenta colored tongue

18. Cheilosis dry scaling of the vermilion surface of the lips and angles of the mouth Angular stomatitis inflammation in the mouth Circumcorneal vascularization Proliferation of the bulbar conjunctival capillaries

19. REFERENCE Vasudevan , D., S, S., & Vaidyanathan , K. (2013). Textbook of biochemistry for medical students . (7th ed., pp. 477-480). New Delhi: Jaypee Brothers Medical Publishers (P) Ltd.

20. Thank you