Characterization and Purification of a Guanidinobenzoatase: A Possible Marker of Human Renal Carcinoma¹

Guanidinobenzoatases are cell surface-associated proteinases supposed to be involved in cancer metastasis, cell migration, and tissue remodeling. The main features of the guanidinobenzoatase associated with human renal carcinoma plasma membrane are weak membrane association, continuous cleavage of p-nitrophenyl-p'-guanidinobenzoate conversely to the site titration effect of this compound when used with trypsin, and a peculiar sensitivity to serine protease inhibitors, compatible with a poorly active form. Plasma membrane preparation followed by agmatine-trisacryl affinity chromatography allows the purification of guanidinobenzoatase to homogeneity with an apparent enrichment factor of 450. Purified guanidinobenzoatase appears as a single polypeptide chain of M_r 80,000, likely stabilized by intrachain disulfides bonds. The properties of purified guanidinobenzoatase indicate that it is an original enzyme in spite of some similarities with plasminogen activators. Indeed, in addition to differences in substrate and inhibitor specificity, guanidinobenzoatase is not recognized by specific monoclonal antibodies directed against plasminogen activators or their single-chain precursors. Thus, human renal carcinoma guanidinobenzoatase appears to be an original enzyme whose activity is undetectable in the nontumoral tissue of origin. In this respect, use of purified guanidinobenzoatase would allow us to obtain specific tools to give new insights in cancer cell metastasis.