Comparative Isoelectric Focusing Properties of Plasminogen Activators From Porcine and Human Tissues

Abstract

Plasminogen activators were isolated from porcine heart, lung and kidney and from human heart and lung. Highly purified porcine heart activator has been shown to have plasminogen activating properties different from human urinary urokinase (UK). The tissue and urinary activators were subjected to isoelectric focusing in granulated dextran gel (Ultradex) over the pH gradient range 3.5 to 11.0, and activator activity was measured by bovine fibrin plate assay. Electrofocusing of Abbott UK revealed isoelectric forms at pI 8.6, 8.8, 9.2, 9.4 and above 9.8, while Serono UK gave forms at 8.2 and 8.6. In contrast, activators from porcine tissues commonly focused at about 7.3, although occasional preparations showed non-symmetrical activity profiles, and focusing of these preparations in a pH gradient 5 to 9 revealed major PI forms at 7.2 and 7.7. Activators from human heart and lung were more closely related to activators from porcine tissues than to UK. Since UK preparations probably contain proteolytically degraded molecules, tissue activators with lower isoelectric points may represent the native molecular forms. Further evidence also indicates that a more catalytically efficient form of tissue activator may be composed of an acceleratory protein and an amidase complexed to a plasminogen activator molecule. (Supported by USPHS NIH Grant HL-15817)

Plasminogen-Activator in Human Early Milk: Its Partial Purification and Characterization

“…The relation between these three components was not determined. According to recent reports, the isoelectric points of tissue activator were at pH 7 .3, ociasionally 7 .2 and 7 .7 (35) ot between 7 and 8 (3 L), of venous occlusion at pH 8.0-8.3 (34) and those of urokinase above pH 8.2 (35). These results suggest that the milk-activator is more closely related to tissue or vascular activator than urokinase.…”