Summary
Filtration through asbestos filter (Seitz) of human plasma modified the prothrombin
molecule as previously shown. Factor II could no longer be activated by physiological
activators (Ca++ + phospholipid + V and Xa) but reacted readily with staphylocoagulase. The separation
and purification of the modified prothrombin allowed the preparation of two fractions:
A small slightly modified accessory fraction, “prothrombin-asbestos- 1”, lost its
ability to be activated by physiological activators, and its ability to be adsorbed
by barium citrate, but retained the immunological reactivity of fragment 1, as well
as the mobility and molecular weight of unmodified prothrombin.
A main fraction, “prothrombin-asbestos-2” appeared to be a modified prothrombin which
has lost its N-terminal extremity. It was not adsorbed by barium citrate and could
not be activated by physiological activators. It possessed a reduced electrophoretic
mobility, as well as a reduced molecular weight (39,000), which are properties similar
to those of thrombin. Both fractions 1 and 2 were devoid of thrombin activity.
Asbestos was thus able to break the prothrombin molecule non enzymatically, the amputation
of the N terminal extremity being responsible for the new functional and physicochemical
properties of the molecule.
Staphylocoagulase appeared not to need the N terminal extremity of the molecule of
prothrombin to form the active thrombin-coagulase complex.
