4. 4
VITAMIN K (PHYLOQUINONE)
It is essential for production of a type of protein
called prothrombin & other factor involve in
blood clotting mechanism. Hence it is known as
anti – hemorrhagic vitamin.
5. • The basic structure of vitamin K is 1,4-
naphtoquinone. Its vitamin activity depends
on the methyl group in position two, while
its fat solubility and other properties are due
to the long side chains. Vitamin K2 is a
collective term for menaquinones with side
chains of different lengths-always with an
iso-prene unit attached.
6. 6
Forms
It is available in 2 forms
K1 – it is the form occurs in plant origin.
K2 - is synthesized by intestinal bacteria.
7. • Phylloquinone (vitamin K1) is present in
variable concentriations in the chloroplasts
or green plants, where it is needed for
photosynthesis. Gram-positive bacteria,
like certain strains of Escherichia coli and
Bacteriodes fragilis produce
menaquinones (vitamin K2),
12. BIOLOGICAL ACTIONS OF VITAMIN-K
1. Vitamin-K is needed for formation of
proconvertin: It is needed for the formation
of prothrombin. Deficiency of vitamin K
decreases proconvertin level in blood.
2. Vitamin-K modifies prothrombin: Vitamin-K
is a coenzyme in modification of
prothrombin to thrombin.
13. 3. Vitamin-K modifies other clotting factors
also: Vitamin K is needed for maintenance
of normal levels of blood clotting factors II,
VII, IX and X.
14. 3. Their conversion to biologically active
forms depends upon vitamin K. The
activation involves carboxylation of
glutamyl residues in the molecules of
these factors (including prothrombin
also) to form dicarboxylic glutamyl
residue.
15. 4. Vitamin-K is needed for carboxylation of
glutamyl residue of Ca++
binding transport
between the flavin coenzyme and the
cytochrome system.
16. FUNCTIONSFUNCTIONS
• Vitamin K is essential for coagulation. Factors II
(Prothrombin), VII (Proconvertin), IX
(Christmas factor), X (Stuart Prower factor)
• Proteins (Zymogens)
»Post Translational modifications
»Functionally active
18. 18
FUNCTIONS
it is essential for the hepatic synthesis of
coagulation factor II, V, VII, IX, X.
CLOTTING – it prevents hemorrhage only in
cases when there is defective production of
prothrombin
OXIDATIVE PHOSPHORYLATION – it
acts as a co- factor in oxidative
phosphorylation associated with lipid
19. FACTORS CAUSING VITAMIN-K
DEFICIENCY:
• Surgical removal of intestine:
• Liquid paraffin:
• Antibiotic therapy for a long time:
• Vitamin-K antagonists: Heparin and warfarin
20. long term administration of antibiotic doses for
more than a week may temporarily suppress
the normal intestinal flora may cause
deficiency of vit k
32. Misuses
• Prolonged consumption of megadoses of
vitamin K (menadione) results in anemia,
which is a reduced level of red blood cells
in the bloodstream.
