VITAMIN K.pptx

Vitamin K, Sources of Vitamin K, RDA of Vitamin K, Biochemical functions of Vitamin K, Dietary Sources of Vitamin K , Hypervitaminosis of Vitamin K

1. VITAMIN K Dr NERUSU SAI PRIYANKA MPT NEUROSCIENCES

2. INTRODUCTION Vitamin K is the only fat soluble vitamin with a specific coenzyme function. It is required for the production of blood clotting factors, essential for coagulation. Vitamin K1 (phylloquinone) is present in plants. Vitamin K2 (menaquinone) is produced by the intestinal bacteria and also found in animals. Vitamin K3 (menadione) is a synthetic form. All the three vitamins (K1, K2, K3) are naphthoquinone derivatives . The three vitamins are stable to heat. Their activity is, however, lost by oxidizing agents, irradiation, strong acids and alkalies .

3. ABSORPTION, TRANSPORT AND STORAGE Vitamin K is taken in the diet or synthesized by the intestinal bacteria. Its absorption takes place along with fat (chylomicrons) and is dependent on bile salts Vitamin K is transported along with LDL and is stored mainly in liver and, to a lesser extent, in other tissues.

4. BIOCHEMICAL FUNCTIONS The functions of vitamin K are concerned with blood clotting process. It brings about the posttranslational (after protein biosynthesis in the cell) modification of certain blood clotting factors . The clotting factors II (prothrombin), VII , IX and X are synthesized as inactive precursors (zymogens) in the liver. Vitamin K acts as a coenzyme for the carboxylation of glutamic acid residues present in the proteins and this reaction is catalysed by a carboxylase (microsomal). It involves the conversion of glutamate (Glu) to gamma -carboxyglutamate ( Gla ) and requires vitamin K, O2 and CO2 . The formation of gamma carboxyglutamate is inhibited by dicumarol , an anticoagulant found in spoilt sweet clover. Warfarin is a synthetic analogue that can inhibit vitamin K action .

5. BIOCHEMICAL FUNCTIONS Vitamin K is also required for the carboxylation of glutamic acid residues of osteocalcin , a calcium binding protein present in the bone. The mechanism of carboxylation is not fully understood. It is known that a 2,3-epoxide derivative of vitamin K is formed as an intermediate during the course of the reaction. Dicumarol inhibits the enzyme (reductase) that converts epoxide to active vitamin K.

6. ROLE OF GLA IN CLOTTING The gamma- carboxyglutamic acid ( Gla ) residues of clotting factors are negatively charged (COO–) and they combine with positively charged calcium ions (Ca2+) to form a complex. The mechanism of action has been studied for prothrombin. The prothrombin Ca complex binds to the phospholipids on the membrane surface of the platelets. This leads to the increased conversion of prothrombin to thrombin.

7. RECOMMENDED DIETARY ALLOWANCE (RDA) Strictly speaking, there is no RDA for vitamin K, since it can be adequately synthesized in the gut. Accordingly, the suggested RDA for an adult is 70-140 Micro g/day .

8. DIETARY SOURCES OF VIT K Cabbage Cauliflower T omatoes A lfa Alfa S pinach and other green vegetables are good sources. It is also present in egg yolk, meat, liver, cheese and dairy products.

9. DEFICIENCY SYMPTOMS V itamin K deficiency may occur due to its Faulty absorption (lack of bile salts) L oss of vitamin into feces (diarrheal diseases) and A dministration of antibiotics (killing of intestinal flora). Deficiency of vitamin K leads to the lack of active prothrombin in the circulation. The result is that blood coagulation is adversely affected. The individual bleeds profusely even for minor injuries. The blood clotting time is increased .

10. HYPERVITAMINOSIS K Administration of large doses of vitamin K produces hemolytic anaemia and jaundice, particularly in infants. The toxic effect is due to increased breakdown of RBC.

11. ANTAGONISTS OF VITAMIN K The compounds—namely heparin, bishydroxycoumarin — act as anticoagulants and are antagonists to vitamin K. The salicylates and dicumarol are also antagonists to vitamin K. Dicumarol is structurally related to vitamin K and acts as a competitive inhibitor in the synthesis of active prothrombin.

12. THANK YOU