vitamin b 12
Download
Skip this Video
Download Presentation
Vitamin B 12

Loading in 2 Seconds...

play fullscreen
1 / 28

Vitamin B12 - PowerPoint PPT Presentation


  • 211 Views
  • Uploaded on

Vitamin B 12. Julie Roche 12/7/04. Vitamin B 12. Cobalamin Porphyrin ring Cobalt Nucleotide Net charge = +1. Vitamin B 12 Derivatives. Cyanocobalamin (digested form) Hydroxycobalamin Chlorocobalamin Methylcobalamin Adenosylcobalamin (5’-deoxyadenosylcobalamin).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Vitamin B12' - elsa


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
vitamin b 12

Vitamin B12

Julie Roche

12/7/04

vitamin b 122
Vitamin B12
  • Cobalamin
  • Porphyrin ring
  • Cobalt
  • Nucleotide
  • Net charge = +1
vitamin b 12 derivatives
Vitamin B12 Derivatives
  • Cyanocobalamin (digested form)
  • Hydroxycobalamin
  • Chlorocobalamin
  • Methylcobalamin
  • Adenosylcobalamin
    • (5’-deoxyadenosylcobalamin)

physiological useful forms

biosynthesis of vitamin b 12
Biosynthesis of Vitamin B12
  • One of the most complicated biosynthetic pathways
  • Involves over 30 enzymes
  • Two pathways
    • Aerobic
    • anaerobic
  • 16 intermediates between uroporphyrinogen III and adenosylcobalamin (aerobic pathway)
difference between pathways
Difference between pathways
  • Need for molecular O2
    • Aerobic: between precorrin-3a and b
  • Point of Cobalt addition
    • Anaerobic: added early, between uroporphyrinogen III and precorrin-2
    • Aerobic: added late, between hydrogenobyrinic acid a,c-diamide and cob(II)lyrinic acid a,c-diamide

*Anaerobic synthesis is more difficult

developments leading to the discovery of the biosynthetic pathway of vitamin b 12
13C labeling (1990)

NMR spectroscopy

Enzymology

Molecular genetics

Developments Leading to the Discovery of the Biosynthetic Pathway of Vitamin B12
vitamin b 129
Vitamin B12
  • Produced on an industrial level
  • Fermentation
    • Methanosarcina
    • Butribacterium
    • Acetobacterium
    • Propionibacterium
      • Produces largest amt of cobalamin
      • Secretes propionic & acetic acid
        • Propionic acid inhibits cobalamin production
vitamin b 12 affects two major pathways
Homocysteine

Methionine

Methylmalonyl CoA

Succinyl CoA

Vitamin B12 affects two Major Pathways
the effects of vitamin b 12 on the conversion of homocysteine to methionine
The effects of Vitamin B12 on the conversion of homocysteine to methionine

Homocysteine

Methionine Synthase

Methylcobalamin

Methionine

5-methyltetrahydrofolate

tetrahydrofolate

Tetrahydrofolate methyltransferase

the effects of vitamin b 12 on the conversion of methylmalonyl coa to succinyl coa
The effects of Vitamin B12 on the conversion of Methylmalonyl CoA to Succinyl CoA

Methylmalonyl Co A

Methylmalonyl CoA mutase

Adenosylcobalamin

Succinyl CoA

Kreb\'s cycle

vitamin b 12 deficiency
Vitamin B12 Deficiency
  • homocysteine and methylmalonyl CoA
  • Increase in methylmalonyl CoA
    • Increased enzyme activity in fatty acid synthesis
      • Build up of odd fatty acids around peripheral nerves
  • Increase in homocysteine
    • Vascular/nervous problems
vitamin b 12 deficiency14
Vitamin B12 Deficiency
  • Excess homocysteine & MMA excreted in urine
    • Diagnosis for cobalamin deficiency
  • Methylmalonyl CoA mutase & Methionine synthase affect amino acid metabolism
    • Amino acid metabolism inhibited by deficiency
vitamin b 12 binding proteins
Vitamin B12 Binding Proteins

Transcobalamin I

Transcobalamin II

Transcobalamin III

transcobalamin i
Transcobalamin I
  • R-type binding protein
  • 33% is carbohydrate
  • Molecular weight = 125,000-150,000
  • Beta globulin
  • Contains more sialic acid than transcobalamin III
  • Carries ~80% of Vitamin B12 in blood
  • Vitamin B12 has half-life of 10-12 days when bound to it
transcobalamin ii
Transcobalamin II
  • Molecular weight = 38,000
  • Alpha globulin
  • NOT a glycoprotein
  • Carries less than 25% of Vitamin B12 in blood
  • Vitamin B12 has half-life of under 1 ½ hours when bound to it
  • Encourages absorption in a number of tissues
  • Degenerates once B12 is released
    • B12 then recirculates
  • Transcobalamin II deficiency results in pernicious anemia
transcobalamin iii
Transcobalamin III
  • R-type binding protein
  • 33% is carbohydrate
  • Molecular weight = 125,000-150,000
  • Alpha globulin
  • Released from granulocytes
  • Contains more fucose than transcobalamin I
antibacterial roles of transcobalamin i iii
Antibacterial Roles of Transcobalamin I & III
  • Binds to large amounts of vitamin B12 and carries it to liver
    • Excreted in bile
  • Prevents bacteria from using the vitamin for growth
slide21

Vitamin B12 separated from

Foods in stomach

Binds to Transcobalamin I

and III

Binds to receptors on

Liver cells

Pinocytosis

Binding Proteins Degraded

Within 1 ½ hrs

Cobalamin

20% excreted in bile

80% binds to BP & reenters blood

BP degenerates, IF binds to

cobalamin

Carried to Ileum and absorbed

in by endocytosis

Released and bound to

Transcobalamin II

Returns to liver or

Carried to other tissues

sources of vitamin b 12
Sources of Vitamin B12
  • Fish
  • Eggs
  • Meat
  • Dairy Products

2.4

vitamin b 12 deficiency24
Vitamin B12 deficiency
  • Cobalamin level in blood = below 200 pg/ mL
  • Common in elderly
causes of vitamin b 12 deficiency
Causes of Vitamin B12 Deficiency

Most Common

  • Malabsorption (inability to absorb food containing cobalamin)
  • Inability to separate cobalamin from food in stomach
  • Lack of recommended intake
  • Inability to use/store cobalamin
  • Proton pump inhibitors
  • Gastritis
  • Stomach/bowel resection
  • Chron’s disease
  • Pancreatitis
  • Gastric lymphoma
  • Myeloma
  • HIV
  • Antibiotics
  • Anticonvulsants
  • Excess Vitamin C
  • Nitric Oxide
symptoms effects of vitamin b 12 deficiency
Symptoms/Effects of Vitamin B12 Deficiency
  • Pernicious Anemia (Vitamin B12 is necessary for RBC production)
  • Lethargy
  • Weight loss
  • Weakness
  • Dementia
  • Leucopenia
  • Thrombocytopenia
  • Axonal degeneration
  • Demyelination
  • Urethral Sphincter problems
  • Depression
  • Alzheimer’s Disease
  • Increased liver weight
  • Fat accumulation around heart, liver, peripheral nerves
symptoms effects of vitamin b 12 deficiency27
Increase

Homocysteine

MMA

Bilirubin excretion

LDH

Liver glycogen

Mitochondrial cristae in liver

Hepatic citrate synthase

Propionic acid

Succinate dehydrogenase

Cytochrome c activity

Propionyl CoA

Amino Acids

Cell metabolism

Protein synthesis

Fatty acid synthesis enzymes

ATP citrate lyase

Causes rise in Kreb’s cycle

Decrease

Transcobalamin II

Intrinsic factor

Symptoms/Effects of Vitamin B12 Deficiency
treatment
Treatment
  • Supplements
    • Oral pills
    • Intramuscular
    • Intranasal
    • Sublingual

1%

500-2000

3-7 days... monthly... 4x year

ad