[Quantitative binding of cysteine-proteinases to a basement membrane: role in their digestion during tumor invasion].

Binding of cysteine-proteinases of the papain-superfamily (papain and cathepsins B, B-like and L) to basement membranes was studied by using the enzymatic activity of these proteinases against their specific fluorogenic substrates. The basement membrane used for these experiments is the bovine lens capsule (weight approximately 50 mg). Papain inactivated by E64 was used in competition experiments, that made it possible to obtain the equilibrium constant, Kd and the number of substrate sites per capsule, n. Values were found around 10(-7) M for Kd, and in the 10(12) range for n. Such results would be of significant interest for the understanding of the biological role of cysteine-proteinases in tumour invasion and other types of tissue remodeling.