4VITAMIN K (PHYLOQUINONE)It is essential for production of a type of proteincalled prothrombin & other factor involve inblood clotting mechanism. Hence it is known asanti – hemorrhagic vitamin.
• The basic structure of vitamin K is 1,4-naphtoquinone. Its vitamin activity dependson the methyl group in position two, whileits fat solubility and other properties are dueto the long side chains. Vitamin K2 is acollective term for menaquinones with sidechains of different lengths-always with aniso-prene unit attached.
6FormsIt is available in 2 formsK1 – it is the form occurs in plant origin.K2 - is synthesized by intestinal bacteria.
• Phylloquinone (vitamin K1) is present invariable concentriations in the chloroplastsor green plants, where it is needed forphotosynthesis. Gram-positive bacteria,like certain strains of Escherichia coli andBacteriodes fragilis producemenaquinones (vitamin K2),
BIOLOGICAL ACTIONS OF VITAMIN-K1. Vitamin-K is needed for formation ofproconvertin: It is needed for the formationof prothrombin. Deficiency of vitamin Kdecreases proconvertin level in blood.2. Vitamin-K modifies prothrombin: Vitamin-Kis a coenzyme in modification ofprothrombin to thrombin.
3. Vitamin-K modifies other clotting factorsalso: Vitamin K is needed for maintenanceof normal levels of blood clotting factors II,VII, IX and X.
3. Their conversion to biologically activeforms depends upon vitamin K. Theactivation involves carboxylation ofglutamyl residues in the molecules ofthese factors (including prothrombinalso) to form dicarboxylic glutamylresidue.
4. Vitamin-K is needed for carboxylation ofglutamyl residue of Ca++binding transportbetween the flavin coenzyme and thecytochrome system.
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
Gamma Carboxylation of GlutamicGamma Carboxylation of Glutamicacidacid
18FUNCTIONSit is essential for the hepatic synthesis ofcoagulation factor II, V, VII, IX, X.CLOTTING – it prevents hemorrhage only incases when there is defective production ofprothrombinOXIDATIVE PHOSPHORYLATION – itacts as a co- factor in oxidativephosphorylation associated with lipid
FACTORS CAUSING VITAMIN-KDEFICIENCY:• Surgical removal of intestine:• Liquid paraffin:• Antibiotic therapy for a long time:• Vitamin-K antagonists: Heparin and warfarin
long term administration of antibiotic doses formore than a week may temporarily suppressthe normal intestinal flora may causedeficiency of vit k
21DAILY REQUIRMENTmen and women – 70 – 140 mcg.children – 35 – 75mcg