Bovine Factors X₁ and X₂: Activation Peptide Based Chromatographic Differences

Bovine Factor X is eluted in two forms (X₁ and X₂) from anion exchange chromatographic columns. These two forms have indistinguishable amino acid compositions, molecular weights and specific activities. The amino acid sequences containing the γ-carboxyglu-tamic acid residues have been shown to be identical in X₁ and X₂, (H. Morris, personal communication). An activation peptide is released from the N-terminal region of the heavy chain of Factor X by an activator from Russell’s viper venom. This peptide can be isolated after activation by gel filtration on Sephadex G-100 under nondenaturing conditions. The activation peptides from a mixture of Factors X₁ and X₂ were separated into two forms by an ion-exchange chromatography. The activation peptide AP₁) which eluted first was shown to be derived from Factor X₁ while the activation peptide (AP₂) which eluted second was shown to be derived from X₂ on basis of chromatographic separations carried out on Factors X₁ and X₂ separately. Factor Xa was eluted as a symmetrical single peak. On the basis of these and other data characterizing these products, we conclude that the difference between X₁ and X₂ are properties of the structures of the activation peptides. (Supported by a grant HL 12820 from the National Heart, Lung and Blood Institute. C.H.J. is an Established Investigator of the American Heart Association).