Summary
Mitochondrial, lysosomal, and microsomal fractions of pig and cow myocardial cells
were screened for their ability to effect lysis of bovine fibrin plates prepared with
Profibrinolysin-containing and profibrinolysin-free reagents. Little if any activity
was observed on profibrinolysin-free fibrin plates. Maximum activity on Profibrinolysin-containing
plates was found in association with the microsomes. Extraction of the microsome preparations
with 0.15 M KCl and 2.0 M KCl dissolved activator molecules with different pH solubility
and stability characteristics. The activator activity of the 2.0 M KCl extract was
in general more stable to acid pH than that of the 0.15 M KCl extract.
The activator characteristic of the microsomal suspensions and of both types of microsome
extracts was stable to acetone precipitation. However, the 2.0 M KCl extract lost
its relatively greater stability to acid pH when precipitated with acetone. The significance
of the chemical environment as a determining factor in final properties of purified
enzyme molecules is discussed. The importance of using a relatively homogeneous cell
population as starting material is also emphasized.
