Summary
A modified method for the isolation and purification of bovine prothrombin is described.
The preparations have a very high specific activity, viz. 3,200 ± 200 u/mg of protein,
show a single symmetrical peak in the analytical ultracentrifuge and by moving boundary
electrophoresis at both pH 6.86 and 8.6. They do not undergo inactivation or dissociation
during electrophoresis at high voltage gradient (7.5) at alkaline pH. Disc electrophoresis
also shows essentially a single component. For optimal activation, prothrombin requires
the presence of factor VII-X complex in addition to factor V.