Identification of a plasma gelatinase in preparations of fibronectin

Preparations of fibronectin purified from human plasma according to conventional methods was found to contain a latent gelatinolytic activity. The protease was activated by exposure to trypsin or electrophoresis in sodium dodecyl sulfate. Zymography of the enzyme under nonreducing conditions gave an estimated Mr of 72,000. Reducing agents destroyed the activity of the enzyme. The gelatinase co-purified with fibronectin in chromatography on Sepharoses conjugated with gelatin, arginine, and heparin but could be separated from fibronectin by gel filtration in a physiological buffer. This protease was found to be a normal constituent of plasma and was probably not derived from the blood cells since the 72-kDa protease was not detected in lysates of these cells.