(Pro)collagenase (matrix metalloproteinase-1) is present in rodent osteoclasts and in the underlying bone-resorbing compartment.

Osteoclasts resorb the extracellular matrix of bone by secreting enzymes and acid into a sealed-off compartment that they form upon attachment to the bone surface. Although the lysosomal cysteine proteinases can degrade collagen after the demineralization of bone at low pH, several lines of evidence suggest that collagenase (matrix metalloproteinase-1, EC 3.4.

Immunoreactive collagenase and bone resorption.

1. Active mouse bone collagenase is excluded from its inhibitory antibody by preincubation of that antibody with various forms of inactive enzyme, e.g.

The simultaneous release by bone explants in culture and the parallel activation of procollagenase and of a latent neutral proteinase that degrades cartilage proteoglycans and denatured collagen.

1. A latent neutral proteinase was found in culture media of mouse bone explants. Its accumulation during the cultures is closely parallel to that of procollagenase; both require the presence of heparin in the media.