Inhibition properties of Sepharose-bound trypsin and a protease on the surface of Ehrlich ascites tumour cells.

Ehrlich ascites cells have been shown to possess a protease with beta-naphthylamidase activity located on the surface of these cells. This enzyme is protected from the inhibitory action of protein inhibitors of trypsin (EC 3.4.21.4) in free solution, but is inhibited by high concentrations of active site-directed inhibitors of trypsin. We believe the protection against inhibition is provided by the location of this protease on the cell surface. We employed a model system of trypsin coupled to Sepharose to demonstrate the protective action of an inert surface, resulting in a marked reduction in inhibition of trypsin-Sepharose, compared to trypsin in free solution, when exposed to both high and low molecular weight inhibitors. This cell protease has been shown to play a role in activation of the zymogen of collagenase exported by tumour cells. This role may have important implications for tumour cell invasion of the intercellular matrix.