Send to

Choose Destination
See comment in PubMed Commons below
Thromb Haemost. 1992 Jun 1;67(6):654-9.

Factor VIIa/tissue factor-catalyzed activation of factors IX and X on a cell surface and in suspension: a kinetic study.

Author information

Department of Medicine, University of California, San Diego.


The kinetics of activation of factor IX and factor X by factor VIIa was studied in the presence of various sources of tissue factor: (1) a surface membrane of human ovarian carcinoma cell line, OC-2008 (2) the cell lysate (of OC-2008) and (3) reconstituted purified human tissue factor. The rates of activation of factors IX and X were monitored in activation peptide release assays using tritiated substrates. The results indicate that the apparent Km values for factor IX and factor X were similar for a given tissue factor, but varied with tissue factor source. The source of tissue factor greatly influenced the apparent differences in Vmax for factors IX and X. When a surface of monolayer provided tissue factor, the Vmax of factor IX was only 2-3 fold lower than factor X, but when either a cell lysate or purified tissue factor was the source of cofactor activity, the difference in Vmax rose to about 8-10 fold. Although, the tissue factor apoprotein in the cells was expressed entirely on the outer surface membrane, the activity of tissue factor on the intact cell surface was 50 to 100-fold lower than in the lysed cell preparation.

[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Loading ...
    Support Center