Proteolytically altered derivatives of plasminogen at tumors of upper respiratory tract

The excessive activation of proteolytic processes is an integral feature of inflammation and cancer. This process leads to the formation of a significant amount of proteolytically damaged proteins. The formation of such derivatives affects noticeably on the course of various physiological processes. In particular, structurally damaged proteolytic enzymes and their pro-forms keep some part of their hydrolytic action and capacity for splitting of other proteins. Contrary to the native proteolysis, such hydrolytic action is not a regular process and lead to generation of the wide variety of proteins' fragments. Because of their structural imperfection, damaged proteases are not subjected to the inactivation by serpin-family inhibitors from blood circulation. On these reasons the formation and accumulation of such protein fragments poses an important component in the pathology. The examples of blood plasma of patients with tumors of the upper respiratory tract and healthy donors were studied by the method of enzyme-phoresis. The existence of SP-domain containing fragments, that at streptokinase activation exhibit fibrinolytic activity, was proved. Formation of such derivatives is the reasonable addition to the formation of well-known kringles-containing fragments of plasminogen (angiostatins). The possible role of such fragments and their possible role in pathologic process are discussed.