Plasminogen activator content of neoplastic and benign human prostate tissues; fibrin augmentation of an activator activity.

The plasminogen activator content of the extracts of excise prostate cancers (25 specimens) was determined with an azocasein assay and found to be on the average 1.7 times higher than that of extracts of excised prostate benign hyperplasias (29 specimens). Both groups contained the same average percentage of human urokinase type activator (approximately 45%) as determined by the inhibition of activity when anti-human urokinase antibody was included in the assay system. The two types of activators were partially purified and found to have distinctly different properties. The most striking difference was the large augmentation of activity o the non-urokinase enzyme in fibrinolysis. The implications of an enhanced fibrinolysis relative to azocaseinolysis (or other) is discussed, particularly with respect to its importance in the quantitation and characterization of activators by different investigators. Highly purified urokinase-like activator was found to be similar to commercial urokinase preparation with respect to molecular weight, isoelectric point, inhibition by the antibody, and inhibition by placenta inhibitor.

Quantitative determination of the binding of epsilon-aminocaproic acid to native plasminogen.

The binding of epsilon-amino[14C]caproic acid (6-aminohexanoic acid, EACA) to native human plasminogen was determined using the ultrafiltration technique of Paulus (Paulus, H. (1969) Anal. Biochem. 32, 91-100) at free ligand concentrations ranging from 2 micrometer to 16 mM. One strong binding site (Kd = 0.009 mM) and approximately five weaker ones (Kd = 5 mM) were found. The constants were obtained by fitting the experimental points to the simple assumption of two sets of noninteracting sites. The distinct separation of the two kinds of sites allowed the correlation of the well known epsilon-aminocaproic acid-induced conformational transition in plasminogen with the saturation of the weaker group of binding sites by this ligand. The conformational transition was monitored by measurements of the sedimentation coefficient, as was done by others earlier. The midpoint of the transition occurred at approximately 3.3 mM free ligand. A dissociation constant of 0.32 mM was also obtained for L-lysine by measurements of the competition between this compound and labeled epsilon-aminocaproic acid for the strong binding site. The correlation between epsilon-aminocaproic acid binding and effects of the compound on various physical and functional properties is discussed. A discussion of the possible sources of error encountered in the technique used is also included.