Abstract
The Vmax/Km (microM -1 min -1.) for bovine factor X activation by bovine factor IXa alpha, in the presence of sufficient [Ca2+] to saturate the initial reaction rate, was 0.007. When factor IXa beta was substituted for factor IXa alpha in this reaction, the Vmax/Km decreased to 0.001, suggesting that factor IXa alpha was a more potent catalyst under these conditions. When phospholipid (PL) vesicles (egg phosphatidylcholine/bovine brain phosphatidylserine, 4:1 w/w) were added to these same systems, at levels sufficient to saturate their effects, little change in the Vmax/Km occurred when factor IXa alpha was the enzyme. However, when factor IXa beta was employed, the Vmax/Km dramatically increased to 0.023, demonstrating that factor IXa beta responded to PL addition to a much greater extent than did factor IXa alpha. Upon addition of thrombin-activated factor VIII (factor VIIIa,t), at a suboptimal level, to the above systems, the Vmax/Km for factor X activation by factor IXa alpha/Ca2+/PL/factor VIIIa,t was increased to 1.0, whereas this parameter for factor X activation by factor IXa beta/Ca2+/PL/factor VIIIa,t under the same conditions was found to be 27.3. During these studies, it was discovered that the factor X which became...Continue Reading
References
Dec 27, 1977·Biochemistry·K Kurachi, E W Davie
Oct 1, 1978·Archives of Biochemistry and Biophysics·R Byrne, F J Castellino
Feb 1, 1977·Thrombosis Research·H SuomelaB Blombäck
Sep 1, 1975·Proceedings of the National Academy of Sciences of the United States of America·K FujikawaE W Davie
Oct 22, 1974·Biochemistry·K FujikawaE W Davie
Dec 19, 1972·Biochemistry·K FujikawaE W Davie
Nov 20, 1973·Biochemistry·K FujikawaE W Davie
Jul 19, 1972·Biochimica Et Biophysica Acta·T F ChuangC Hougie
Mar 1, 1983·Biochemistry·R P Link, F J Castellino
Jan 5, 1982·Biochemistry·G W AmphlettF J Castellino
Apr 1, 1982·The Journal of Clinical Investigation·M B Hultin
Aug 1, 1982·Thrombosis Research·M J GriffithH R Roberts
Apr 15, 1982·Archives of Biochemistry and Biophysics·R P Link, F J Castellino
Feb 5, 1980·Biochemistry·G A Vehar, E W Davie
Feb 1, 1964·Biochemistry·H S KINGDONO D RATNOFF
Citations
Jun 1, 1993·British Journal of Haematology·G Kemball-CookT W Barrowcliffe
Jan 1, 1985·The Journal of Clinical Investigation·M J GriffithH R Roberts
Apr 14, 2009·Biological Chemistry·Thomas Zögg, Hans Brandstetter
Jan 29, 1985·Biochemistry·S A Steiner, F J Castellino
Dec 31, 1985·Biochemistry·M E JonesB R Lentz
Nov 1, 1983·Archives of Biochemistry and Biophysics·R P Link, F J Castellino
Mar 24, 1995·The Journal of Biological Chemistry·D BharadwajK J Smith
Feb 1, 1989·Archives of Biochemistry and Biophysics·J M BealsF J Castellino