Functions of vitamin b12

1. Presented by
Akshaya Anil
2nd Semester M. Sc
Biochemistry
Dept.of Biochemistry
Kerala University

2. Vitamin B 12
 Water soluble
 Only metal containing vitamin
 Central metal atom is cobalt
 Also known as cobalamin, anti pernicious
anemia vitamin
 RDA
 Adult - 2 micrograms per day
 Preganancy/lactation - 3 micrograms/day

3. Sources
Food of animal origin
Liver, kidney, milk, curd, egg, fish
Syntheised exclusively by
microorganisms
3-5 grams is stored in liver is sufficient
to last upto 5 years

4. Absorption
Absorption is mediated by receptor
sites in ileum, that require, it to be
bound with a glycoprotein,intrinsic
factor.
 Transcobalamin 2 is needed for
transport to tissue.
 Transcobalamin 1 bound to store in
liver.

5. Structure

6. Different forms
R group Cobalamin
Cyanid Cyanocobalamin
Water Aquacobalamin
Hydroxyl Hydroxycobalamin
Methyl Methylcobalamin
Adenosylcobalamin 5-
deoxyadenosylcobalamin

7. Active coenzyme forms
Coenzyme Enzyme Funtion
Methylcobalamin
Methionine
synthase
Synthesis of
methionine from
homocysteine
5
deoxyadenosyl
cobalamin
Methyl malonyl
CoA mutase
Converts
methylmalonyl
CoA to succinyl
CoA
5
deoxyadenosyl
cobalamin
Methionine
synthase
reductase
Converts
homocysteine
back to
methionine

8. 5 deoxyadenosylcobalamin
Reaction catalysed by
methylmalonylmutase

9. Methyl malonyl CoA

10. Reactions involved

11. Methylcobalamin
Reaction catalysed by methionine synthase

12. Role of folate

13. Important roles
• Promotes maturation of erythoid cells
• Increase WBC count and platelet count
• Stimulates appetite and general health
• Cures neurological symptoms of
pernicious anaemia

14. Deficiency diseases
• Deficiency leads to pernicious anaemia
chacterised by
• Low hb levels
• Decreased no.of RBCs
• Neurological manifestations

15. References
• Enzymes, Malcolm Dixon
• Harper's Biochemistry, Robert K.
Murray
• Biochemistry, Judith & Donald Voet
• Lehninger Principles of Biochemistry