Warfarin acts by inhibiting all of the following factors except: March 2005

Ans. A: Factor III Warfarin inhibits the vitamin K-dependent synthesis of biologically active forms of the calcium-dependent clotting factors as well as the regulatory factors protein C, protein S, and protein Z. They interfere with regeneration of the active hydroquinone form of vitamin K which carries out the final step of gamma carboxylating glutamate residues of prothrombin and factors VII, IX and X. Other proteins not involved in blood clotting, such as osteocalcin, or matrix Gla protein, may also be affected.