Vitamin K is a fat-soluble vitamin that acts as a coenzyme in the coagulation process. It exists in three forms: K1 from plants, K2 from intestinal bacteria and animals, and K3 which is synthetic. Vitamin K is important for the carboxylation of clotting factors II, VII, IX, X and proteins C and S in the liver. This carboxylation adds a negative charge that allows the clotting factors to bind to platelet membranes and interact efficiently to form blood clots. Vitamin K deficiency can result from fat malabsorption, broad-spectrum antibiotics that kill gut bacteria, or excessive loss of vitamin K in the feces, leading to bleeding disorders

1. VITAMIN
‘K’

2. Introduction
üWater soluble vit has many coenzyme fxn, BUT Vit Kà only fat soluble
vit with coenzyme.
üHas role in coagulation process.
üExist in 3 different form:
• Vit. K1( phylloquinone): plant, green veg.
• Vit K2( menaquinone): intestinal bacteria & animal.
• Vit K3( menadione): is a synthetic formà can be metabolized to
phylloquinone.

3. Further……….
• Isoprenoid unit is present ( K1 and K2)
• Stable to heat.
Dietary sources:
Good sources: Cabbage, cauliflower,
tomatoes, spinach & green vegetables.
Also +nt: egg yolk , meat , liver, cheese
& milk products.

4. Absorption, transport and storage
• Diet or intestinal bacteriaà vit K
• Absorption is taken place in +nce of chylomicrons & bile salts.
• Transported along with LDL & stored in liver.
• Little in other tissue.
RDA: Strictly speaking à no RDA, since it can be synthesized in GUT
by flora.
However, recommended ( ½ by diet & ½ by bacterial flora)
Accordinglyà suggested à RDA: 70-140 𝜇g/day.

5. Function: mainly in clotting process
• Post translational modification of II, VII, IX, X & protein C and S
zymogens ( inactive precursors)à activeà coagulation process.
• Modification: acts as COENZYME for the carboxylation of glutamate aa of
above factors à γ-carboxyglutamate (Gla)à which chelates the calcium
ionà binds to platelet membrane
• Vit k dependent factors: II, VII, IX ,X AND Protein C& S.
• Also require for carboxylation of osteocalcin à calcium binding protein in
bone

6. Role of Gla in clotting
• γ-carboxyglutamate (Gla) à neg charge (coo-).
• Binds with +ve ca++, which in turn binds with phospholipids (-ve) on
membrane surface of platelets.
• Brings the clotting factor together àmore interaction betwn themà
action become more efficient on platelets platform

8. • Dicumarol ( natural) & warfarin ( synthetic)à reduce blood clot.
• After carboxylation, vit k ( HQ) is converted à 2,3 epoxide form
• Which is converted by epoxide reductase à to Quinone
• Quinone by another reductase à to vit K(HQ) again to become active
• Dicumarol & warfarinà inhibits epoxide reductase.
Antagonist of vit K
• deep vein thrombosis,
• pulmonary embolism,
• heart attack,
• stroke

9. A high dose of vit K is the antidote to an
overdose of warfarin
• If enough vitamin K (a quinone) is givenà by diet,
• Get reduced to the active hydroquinone by the warfarin-
insensitive enzyme, and carboxylation can continue,

10. Deficiency symptoms
üCauses
• Fat malabsorption
• ↑↑ broad-spectrum antibiotics ( killing of gut flora)
• Loss of vit. K in feces (diarrhea)
üLeads to ( ↓↓ active prothrombin)
• Bleeding disordersà profusely bleeds even for minor injury.
üHypervitaminosis: ↑↑ RBC destructionà
anemia & jaundice

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