Identification of acid proteinase activity in the ascites fluid of mouse teratocarcinoma

A mouse teratocarcinoma in our laboratory recently converted from a slow growing multicellular form (embryoid body) to an apparantly more malignant fast growing single cell form. Associated with this conversion was an accumulation of ascites fluid in which acid proteinase activity was found to be present. Inhibitor studies allowed identification of this proteinase activity as the carboxyl peptidase Cathepsin D. Mouse Cathepsin D has a pH optimum of 3.0 and is inactive at pHs higher than 5.0. Titrations of Cathepsin D by the specific inhibitor Pepstatin A yielded estimations for the amount of Cathepsin D present in the ascites fluid. These studies set the ground work for investigations into the possible role of proteinases in malignant transformation.

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