This document discusses vitamin K and its functions. It notes that vitamin K includes vitamin K1, K2, and K3. Vitamin K1 is found in plants, K2 is produced by bacteria, and K3 is synthetic. Vitamin K plays an important role in blood clotting by acting as a cofactor for carboxylation of clotting factors in the liver. It is also involved in calcium binding and bone mineralization through carboxylation of proteins in bone. A deficiency in vitamin K can cause bleeding disorders and osteoporosis.

1. SIMS 305- Clinical Biochemistry
Dr. Ali Raza
Senior Lecturer
Centre for Human Genetics and Molecular Medicine (CHGMM),
Sindh Institute of Medical Sciences (SIMS), SIUT.
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2. Vitamin K
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3. Sources of vitamin K
Vitamin K is abundant in the diet.
• Green leafy vegetables
• vegetable oil
• broccoli
• cereals
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4. Vitamin K
Vitamin K1(Phylloquinone) Vitamin K2 (Menaquinone)
Vitamin K3 (Menadione)
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5. Vitamin K
• Vitamin K is a group of lipophilic,
• Contains naphthoquinone ring and
an aliphatic side chain.
Vitamin K1(Phylloquinone)
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6. Vitamin K
• Vitamin K1 (phylloquinon) – Plant origin
• Vitamin K2 (menaquinon) – Produced by bacteria in the
large intestine
• Vitamin K3 (menadione)- synthetic analogue of vitamin K
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7. Vitamin K
• K1 and K2 are used differently in the body
• K1 – used mainly for blood clothing
• K2 – important in non-coagulation actions -
as in metabolism and bone mineralization, in cell growth,
metabolism of blood vessel walls cells.
• K3 is three times more potent than natural varieties. It is
water-soluble.
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8. Vitamin K - function
Blood Coagulation :
• Needed for the post-translation modification of proteins
required for blood coagulation
• Vitamin K is first converted to its hydroquinone form in liver
microsomes by dehydrogenase using NADPH.
• Act as Cofactor of liver microsomal carboxylase
• which carboxylates glutamate residues to carboxyglutamate
during synthesis of prothrombin and coagulation factors VII, IX a
X (posttranslation reaction).
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9. Vitamin K - function
• All the first ten glutamate residues of prothrombin are first
carboxylated by vitamin K.
• The γ-carboxyglutamate residues now provide calcium
binding sites in the N-terminal portion.
• This brings together activated factor and accelerin close to
the phospholipid membrane of platelets.
• This enhances blood coagulation manifold.
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11. Vitamin K
Calcium Binding Proteins:
• Carboxylate glutamate residues of Ca++ binding proteins of
bones, spleen, placenta and kidneys.
• This enhances the capacity of these proteins to deposit calcium
in the tissues
3. Role in Oxidative Phosphorylation
• Necessary cofactor in oxidative phosphorylation being associated
with mitochondrial lipids.
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12. Vitamin K - deficiency
• Deficiency is caused by
(a) Fat Malabsorption
(b) Liver failure
• Blood clotting disorders – dangerous in newborns,
life-threatening bleeding (hemorrhagic disease of the
newborn)
• Osteoporosis due to
failed carboxylation of osteocalcin
decreased activity of osteoblasts.
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