Purification of human brain tissue factor.

Tissue factor (factor III) is a lipoprotein cofactor which markedly enhances the catalytic effect of coagulation factor VIIa upon factors IX and X. Human tissue factor apoprotein was purified 53,000-fold to homogeneity from brain using acetone delipidation, Triton X-100 extraction, and affinity chromatography upon factor VII-agarose. The purified apoprotein has an apparent molecular weight of 44,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, an amino acid composition similar to bovine brain tissue factor, and an NH2-terminal amino acid sequence of Ser-X-Asn-Thr-Val-Ala-Val-Tyr-X-Tyr-X-Leu-Lys-(Ser)-Lys-Asn-Phe. Optimal relipidation of the tissue factor apoprotein was associated with a 5000-fold enhancement of clotting activity and occurred at a phospholipid/apoprotein (w/w) ratio of greater than 600.