DIFFERENTIAL COMPETITIVE-INHIBITION OF A CELL-SURFACE PROTEASE ON NORMAL EPITHELIAL-CELLS AND CARCINOMA-CELLS OF THE COLON

The cell surfaces of normal colonic epithelial cells and colonic carci noma cells both possess a protease referred to as guanidinobenzoatase (GB). Previous studies have shown that these cells possess two distinc t isoenzymic forms of GB which could be distinguished by their selecti ve recognition of cytoplasmic protein inhibitors of GB. in the present study we have used competitive inhibitors of GB to demonstrate the di fferential inhibition of the GB on normal colonic epithelial cells whi lst the GB on colonic carcinoma cell surfaces remains active. The enzy mic status of GB on these cells has been determined by challenging the treated cells in frozen sections with a second fluorescent inhibitor, followed by fluorescence microscopic analysis.