Inhibition of guanidinobenzoatase: evidence for multiple forms of this protease on different tumour cells.

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. 9-Aminoacridine is a competitive inhibitor of this enzyme and has been used to locate cells possessing this enzyme in wax embedded sections by means of fluorescent microscopy. Naturally occurring inhibitors of guanidinobenzoatase can be extracted from different tissues. These inhibitors show selectivity in their ability to inhibit the binding of 9-aminoacridine to different types of tumour cells which have invaded human liver tissue. Inhibition is non-competitive and reversible. The results indicate that guanidinobenzoatase exists in a number of different forms on the surface of different tumour cells. These different forms of the enzyme were recognised by inhibitors obtained from different organs. It is suggested that these inhibitors may have a regulatory role in tumour cell migration.