A collagenase was purified from homogenates of V2 ascites-cell carcinoma growing in rabbit muscle. (NH4)2SO4 precipitation, ion-exchange and gel-filtration chromatography, and affinity chromatography (by using the CB7 CNBr) cleavage fragment of α1(I) collagen linked to agarose) gave a 268000-fold purification and a sevenfold increase in total enzyme units recovered. The specific activity, defined as μmol of collagen in solution cleaved/h per mg of enzyme at 35°C, WAS 1.74.2. The collagenase had a broad pH optimum from pH7.0 to 9.5, and a mol.wt. of between 33000 and 35000. It was inhibited by dithiothreitol, L-cysteine, D-penicillamine, EDTA and 1,10-phenanthroline, and by both rabbit and human serum. 3. Removal of cations by a chelating resin (Chelex 100) produced as inactive enzyme that could be reactiviated by the addition of Ca2+ ions at concentrations as low as 1μM. Other bivalent cations were not effective. 4. The purified collagenase cleaved peptides α2 and α1-CB7 (denatured polypeptides of collagen) at 37 degrees C at one site only. [α1 (I)]2α2 and [α1(III)]3 collagens in solution were cleaved at the same site approximately five times more rapidly than [α1 (II)]3. 5. An inhibitor of the enzyme in the tumour extracts, which was dissociable from the enzyme at the (NH4)2SO4 precipitation step of purification, had a mol. wt. of between 40000 and 50000 but was distinct from the α1 trypsin inhibitor. 6. Studies with zonal density-gradient centrifugation suggested that the enzyme was bound to fibrillar substrate (collagen) extracellularly, but that it was not associated with enzymes originating in cell mitochondria, microsomal preparations or lysosomes.
The Nature of the Muscle-Relaxing Factor
