Figure 4.

Hydrolysis of Congo Red-labeled elastin and fluorescein-conjugated collagens. Bovine skin DQ-collagen I, human placenta DQ-collagen IV, and elastin-Congo Red were incubated with cathepsins K, L, and their respective S2 mutants as described in Materials and Methods. Collagenolytic activities were measured by monitoring the fluorescence release (excitation wavelength: 395 nm; emission wavelength: 415 nm). After removal of the uncleaved substrate, the elastinolytic activity was deduced from the absorbance of soluble released dye (λ = 490 nm). Proteolytic activities were expressed as normalized values (%), using wild-type cathepsin K as reference. The results (triplicate assays) are means ± SEM.