Notes on Vitamins

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Water-soluble Vitamins:

• Biotin deficiency caused by excessive consumption of raw eggs.

• Enzymes: pyruvate carboxlase, acetyl CoA carboxylase, propionyl CoA carboxylsae.

• Findings: alopecia, bowel inflammation.

Thiamine (B1) Deficiency:

• Alcoholism.

• Findings: Wernike, Korsakoff, wet and dry beri-beri.

• Enzymes: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase.

Niacin (B3) Deficiency:

• Pellagra: diarrhea, dementia, dermatitis, and even death.

• Enzymes: dehydrogenases.

Folic acid Deficiency:

• Alcoholics and pregnancy.

• Homocystinemia, magaloblastic anemia, and neural tube defects.

• Enzymes: thymidylate synthase.

Cyanocobalamin (B12) Deficiency:

• Enzymes: homocysteine methyltransferase, methylmalonyl CoA mutase.

• Caused by pernicious anemia, aging, poor nutrition, bacterial overgrowth, Crohn's disease, etc.

• Findings: megaloblastic anemia, and progressive peripheral neuropathy.

Pyridoxine (B6) Deficiency:

• Enzymes: aminotransferases, AST/GOT, ALT/GPT, delta-aminolevulinate synthase.

• Caused by isoniazid therapy.

• Findings: sideroblastic anemia, cheilosis, and convulsions.

Riboflavin (B2) Deficiency:

• Enzymes: dehydrogenases.

• Findings: corneal neovascularization, cheilosis, and magneta-colored tongue.

Ascorbate (vitamin C) Deficiency:

• Enzymes: prolyl and lysyl hydroxylases, and dopamine hydroxylase.

• Caused by lack of green vegetables and citrus fruits.

• Findings: scurvy; proline and lysine residues are not hydroxylated, hydrogen bonding within the triple repeats does not take place.

Pantothenic Acid:

• Deficiency is rare.

Lipid-Soluble Vitamins:

Vitamin D:

• Normalizes calcium levels; deficiency leads to rickets.

Vitamin A:

• Vision; deficiency leads to night blindless.

Vitamin K:

• Carboxylation of glutamic acid residues in Ca2+ binding proteins, and coaglation factors-II, VII, IX, and X; deficiency leads to increased PT, bleeding, and easy bruising.

Vitamin E:

• Antioxidant; prevents oxidation of LDLs.

Calcium Homeostasis:

• Hypocalcemia causes release of PTH causes conversion of Vitamin D to 1,25-DHCC (dihydroxycholecalciferol or calcitriol), which causes Ca uptake in GI tract.

• 1,25-DHCC: also causes Ca reabsorption in kidney.

Synthesis and Activation of 1,25-Dihydroxycholecalciferol (Calcitriol):

• 7-Dehydrocholesterol activated by UV in skin produces cholecalciferol (D3).

• 25-Hydroxylation in liver of cholecalciferol produces 25-Hydroxycholecalciferol; patients with liver failure need 25-DHCC or 1,25-DHCC.

• PTH causes 1alpha-hydrolylation in kidney producing 1,25-Dihydroxycholecalciferol (calcitriol).

Vitamin D Toxicity:

• Hypercalcemia: impaired renal function.

• Vit D is stored in the liver, promoting absorption of Ca and Ph.

• Exacerbates osteoporosis.

• Polyuria, polydipsia, nocturia.

Vitamin D Deficiency:

• Rickets in children; osteomalacia in adults.

Vitamin A:

• Vision.

• Vitamin A is stored in the lover.

• Deficiency causes night blindness, dry eyes, bronchitis, pneumonia.

Three Types of Vitamin A:

• C-1: hydroxyl (retinol).

• Carboxyl (retinoic acid).

• Aldehyde (retinal).

Vitamin K:

• Required to create Ca2+ binding sites on Ca-dependent proteins.

• This is done by gamma-carboxylation of glutamyl residues.

• This is done while the protein is being translated on ribosomes.

• These proteins include: coagulation factors II, VII, IX, X, and anticoagulant proteins C and S.

• Deficiency caused by prolonged use of antibiotics.

• Findings: increased PT, hemorrhagic disease with no connective tissue problems.

Vitamin C Deficiency:

• Findings: normal PT, gum hyperplasia, loss of teeth, anemia; caused due to vitamin C deficiency in diet.

Vitamin E:

• Antioxidant.

• Prevents peroxidation of fatty acids in cell membranes; prevents oxidation of LDL.

• Deficiency: hemolysis, neurologic problems, retinitis pigmentosa.

Additional Notes:

• Amitriptyline: causes riboflavin deficiency.

• Nicotinic acid (niacin): prevents hepatic synthesis of VLDL; used to treat hyperlipoproteinemias.

• Vitamin A deficiency: also causes acne due to bad health of epithelial tissue; give 13-cis-retinoic acid.

• 11-cis-retinal (vitamin A) deficiency: night blindness.

Additional Readings:

Basic Biochemistry

1. Nucleic Acid Structure and Organization
2. DNA Replication and Repair
3. Transcription and RNA Processing
4. Genetic Code, Mutations, and Translation
5. Genetic Regulation
6. Recombinant DNA
7. Amino Acids, Proteins, Enzymes
8. Hormones
9. Vitamins
10. Energy Metabolism
11. Glycolysis and Pyruvate Dehydrogenase
12. Citric Acid Cycle and Oxidative Phosphorylation
13. Glycogen, Gluconeogenesis, and Hexose Monophosphate Shunt
14. Lipid Synthesis and Storage
15. Lipid Mobilization and Catabolism
16. Amino Acid Metabolism Disorders
17. Purine and Pyrimidine Metabolism
18. Electron Transport
19. Citric Acid Cycle and Glyoxylate Cycle
20. Glycolysis
21. Pyruvate Metabolism
22. Mitochondrial ATP formation
23. Gluconeogenesis
24. Glycogen Metabolism
25. Nitrogen Fixation (Metabolism) reactions, and Heme Metabolism
26. Amino Acid Metabolism
27. What is Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD)?

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