Vit b12

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 iscobalt
Also known ascobalamin, 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 2is 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 topernicious 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