Integration of human plasminogen or streptokinase into stable complexes with oxidoreductases and pyruvate kinase

The formation of stable equimolar complexes ofstreptokinase or plasminogen with muscle lactatedehydrogenase or pyruvate kinase, heart mitochondrialmalate dehydrogenase and hepatic catalase at pH 7.4,3.0 and 10.0 was first detected by differentialspectroscopy methods. All complexes, except those ofplasminogen with dehydrogenases, were resistant to 6 Murea. Judging from circulardichroism spectra, tertiary and secondary structureswere considerably changed in the complexes. Thesechanges were significantly dependent upon the natureof interacting proteins; in some cases theirstructures were more ordered. NAD (but not NADH)hampered the formation of streptokinase complexes withdehydrogenases. The plasminogen–activating function ofstreptokinase and the ability of plasminogen to beactivated by streptokinase in the complexes withoxidoreductases were essentially unchanged.Pyruvate kinase induced a moderate (by 35%) increasein the streptokinase activating function. It isassumed that the formation of complexes ofstreptokinase or plasminogen with enzymes may serve asa link in metabolic regulation and/or intercellular interactions.