About vitamin kfat soluble vitamin, antihemorrhagic.mechanism of action of vitamin kphytonadione (vitamin k1) is a synthetic form of vitamin k and is lipid soluble. vitamin k acts as a cofactor in the synthesis of coagulation proteins- prothrombin, factors vii, ix, and x by liver. vitamin k dependent changes in the final stage of synthesis of these coagulation proteins is gama-carboxylation of glutamate residues of these zymogen proteins and their descarboxy-forms converted in to active forms- which confers on them the capacity to bind ca2+ and to get bound to the phospholipid surfaces which are essential properties for participation in the coagulation cascade.