Design of fluorescent probes for an enzyme on the surface of tumour cells.

The proteolytic enzyme guanidinobenzoatase is specific for arginyl peptide bonds and is capable of degrading fibronectin. This enzyme is associated with the cell surface of tumour cells in formaldehyde-fixed wax-embedded sections of human pathological tissue. We have designed fluorescent probes for the active site of guanidinobenzoatase: these probes act as competitive inhibitors and can be used to locate cells possessing guanidinobenzoatase. The processes of designing probes, testing their potential as inhibitors, and applying these probes to tumour cell location, all depend upon affinity principles.