Isolation and characterization of bovine factor XI (plasma thromboplastin antecedent).

Factor XI (plasma thromboplastic antecedent) has been purified approximately 28 000-fold from bovine plasma with an overall yield of about 30%. The isolation procedure involves barium sulfate adsorption of contaminants, ammonium sulfate precipitation, and chromatography on heparin-agarose, CM-Sephadex, and DEAE-Sephadex. The final product was homogeneous when examined by polyacrylamide gel electrophoresis and immunoelectrophoresis. A minimal mol wt of 124 000 was determined by sedimentation equilibrium. Factor XI is composed of two similar or identical polypeptide chain (mol wt of approximately 55 000), and these two chains are held together by a disulfide bond(s). Factor XI is a glycoprotein which contains approximately 11% carbohydrate including 5.4% heose, 4.7% N-acetylhexosamine, and 1.0% N-acetylneuraminic acid. Other properties of this coagulation factor including its amino acid composition and inhibition by antibodies prepared in rabbits are also reported.