Vitamins and Coenzymes 2

Vitamins and Coenzymes 2

Vitamins and Coenzymes 2

1 of 21

Vitamin B9 - Folic Acid

  • Source: Liver, kidney, yeast, lemons, bananas, strawberries and fresh green vegetables
  • Content reduced 50-90% by cooking, also light sensitive

2 of 21

Vitamin B9 - Folic Acid

  • Biological function: Folic acid reduced to tetrahydrofolate (THF; coenzyme F) by two enzymes using NADP as a coenzyme
  • THF used to transger hydroxymethyl, formyl and methyl groups in a large number of reactions and significantly in the synthesis of purine and pyrimidine bases in the formation of DNA
3 of 21

Vitamin B9 - Folic Acid Deficiency

  • Caused by inadequate diet (body reserves are low), malabsorption, malignant disease, medication, alcohol abuse
  • Megablastic anaemia: due to faulty red blood cell multiplication and maturation. Treatment with 5-20mg folic acid daily
  • Supplements given in pregnancy, leukaemia and drug-induced folate deficiency. Prophylaxis with 0.2-0.5mg folic acid daily
  • Supplements may mask B12 deficiency which results in damage to the nervous system
4 of 21

Vitamin B12 - Cyanocobalamin

  • Found in meat, shellfish, salmon, milk, cheese, eggs, fortified breakfast cereals
  • Daily requirement only 1.5mg
  • Forms the basis of two unstable coenzymes required in intramolecular rearrangement reactions
  • Essential (with folic acid) for normal erythropoiesis
  • Deficiency causes pernicious anaemia and degeneration of spinal cord
5 of 21

Vitamin B12 - Cyanocobalamin

6 of 21

Vitamin C - Ascorbic Acid

  • Source: citrus fruits, green plants, tomatoes, potatoes
  • Can be oxidised on cooking
  • Water soluble

7 of 21

Vitamin C - Ascorbic Acid

  • Biological function: most powerful reducing agent known to occur naturally in living tissue, cofactor in numerous processes
  • Collagen
    • Most common protein in vertebrates as the major fibrous element of skin, bone, tendon, cartilage, blood vessels and teeth
    • Contains two amino acids present in very few other proteins - hydroxyproline and hydroxylysine
    • The hydroxyproline in collagen is synthesised from proline
  • Ascorbic acid maintains the iron atom (present at the active site of prolyl hydroxylase) in the ferrous state (Fe2+)
8 of 21

Vitamin C - Ascorbic Acid

  • The hydroxylation of proline is essential to provide more OH groups for H bonding which maintains the stability of the triple helix of collagen
  • Hydroxylation of dopamine to noradrenaline
  • Hydroxylation in steroid synthesis
  • Electron donor in the conversion of folic acid to THF
  • Iron absorption (Fe3+ to Fe2+)
  • Antioxidant
  • Role in fighting infection and in wound healing
  • Possible reduced levels apparentin the common cold and cancer
9 of 21

Vitamin C - Ascorbic Acid Deficiency and Toxicity

  • Scurvy characterised by swollen gums, bruising, haemorrhage, bone fracture, loose teeth, poor wound healing, anaemia
  • Clinical trial on the effect of citrus juice on scurvy conducted on British sailors in 1747
  • Supplements may benefit those not following a balanced diet (elderly, infirm), diabetics, pregnant and lactating women, heavy drinkers and smokers
  • Toxicity: stomach complaints
10 of 21

Vitamin A - Retinol

  • Source: milk, butter, cheese, liver (especially cod liver oil), added to margarine
  • Retinol can be synthesised from carotenoids (found in carrots and tomatoes)

11 of 21

Vitamin A - Retinol

  • Biological Function: converted to 11-cis-retinol (using NADP+ as a coenzyme) which is a photosensitive prosthetic group essential for normal retinal functional
  • Vitamin A also has a role in the maintenance of normal growth, bone formation, repair of epithelial tissue and reproductive ability
12 of 21

Vitamin A - Retinol Deficiency and Toxicity

  • Still widespread in developing world
  • Night blindness, dry and hyperkeratotic skin (retinoic acid used as psorioasis/acne treatment), skin infection, corneal damage and blindness
  • Supplements may be required in breast feeding women to compensate for infant's supply and in patients unable to absorb or store lipids
  • Toxicity: unborn children
13 of 21

Vitamin D

  • Vitamin D2 (calciferol, ergocalciferol)
  • Vitamin D3 (cholecalciferol)
  • Vitamin D4
  • Source: Cholecalciferol present in butter, milk, cheese, egg yolk and fish liver oils, added to margarine and baby foods
  • Body not dependent on dietary intake as vitamin D3 is formed under UV light from provitamin precursors (7-dehydrocholesterol) in the skin

14 of 21

Vitamin D

  • Biological function
    • Vitamin D is converted into active metabolites in the liver and kidney
    • The metabolites stimulate synthesis of specific proteins that act as Ca2+ carriers in bone and intestine increasing absorption of dietary Ca2+ and release of Ca2+ from bone (PO4- passively accompanies the Ca2+ movements)
    • Vitamin D maintains Ca2+ and PO4- at sites of new bone formation therefore is essential for proper formation of the skeleton
15 of 21

Vitamin D Deficiency and Toxicity

  • Rickets in children characterised by distortion of the long bones of the legs and bones of the pelvis and spine
  • Osteomalacia in adults (bone softening)
  • Rate of synthesis of vitamin D in the skin depends on exposure to UV light therefore night workers and miners traditionally prone to deficiency
  • Rate of synthesis of vitamin D in the skin also depends on skin pigmentation
  • Toxicity: weakens the bones
16 of 21

Vitamin E

  • Vitamin E = family of compounds (the tocepherols and tocotrienols)
  • Source: vegatable oils (sunflower, soybean and corn oil)

17 of 21

Vitamin E

  • Biological function
    • Acts as a fat-soluble antioxidant
    • Also involved in the function of nerve and eye tissue
  • Deficiency
    • Haemolytic anaemia
    • Neuromuscular and neurological problems (e.g. myopathies)
    • Eye problems (e.g. retinopathy)
  • Toxicity
    • Muscle weakness, fatigue, nausea and diarrhoea
    • The most significant risk is bleeding
18 of 21

Vitamin K

  • Vitamin K1 (phylloquinone)
  • Vitamin K2 (manoquinone)
  • Source: leafy green vegetables (spinach, cabbage, kale), gut flora can convert K1 into K2

19 of 21

Vitamin K

  • Biological functions: attaches a second carboxylic acid group onto the glutamate residues of a number of proteins to form a gamma-carboxyglutamate (Gla) residue
  • This activates blood coagulation factors II (prothrombin), VII, IX and X, the anticoagulant proteinsC and S and protein Z
  • Warfarin acts as a vitamin K1 antagonist
  • Function of K1 and K2 identical
20 of 21

Vitamin K: Deficiency and Toxicity

  • Deficiency
    • Rarely due to lack of dietary intake
    • Malabsorption conditions can affect uptake
    • Symptoms include anaemia, bruising and bleeding at the mucosal membranes (e.g. gums, nose)
  • Toxicity
    • Unlike most fat-soluble vitamins, not stored in great quantities in the liver
    • Therefore toxicity is not seen with higher doses of vitamin K1 or K2 in otherwise healthy people
21 of 21

Comments

No comments have yet been made

Similar Pharmacy resources:

See all Pharmacy resources »See all PH1123 resources »