This 1996 lab study tested whether collagenase-3 (MMP13) can cut aggrecan, the large molecule that holds water in cartilage. It did, in the region where other enzymes cut it: at the site already known for other MMPs, and at a second site that had not been seen before for any proteinase.
Aggrecan is the large proteoglycan that holds water in cartilage and lets it resist compression. It has a stretch called the interglobular domain, between two folded regions, where several enzymes are known to cut. Earlier work had shown MMP13 is the major MMP made by cartilage cells when retinoic acid prompts them to break down their matrix. The researchers set MMP13 against an aggrecan substrate and mapped exactly where it cut.
MMP13 cleaved aggrecan in the interglobular domain at the site already identified for other members of the MMP family, after amino acid 314. It also cut at a new site, after amino acid 384, that had not previously been seen for any other proteinase. The authors note that MMP13 is the major MMP expressed by chondrocytes stimulated with retinoic acid to degrade their matrix.
This is a short report of a test-tube experiment. It shows MMP13 can cut aggrecan, not how much aggrecan loss in real cartilage is due to MMP13 rather than the aggrecanases such as ADAMTS5. The abstract reports where it cut, not how fast, and the study did not look at cartilage tissue, animals or people.
MMP13 is known for cutting collagen, but this study shows it can also cut the other main component of cartilage. That matters for reading MMP13 research: an enzyme that cuts both type II collagen and aggrecan can act on the whole matrix, not just its fibres.
Yes. Besides type II collagen, MMP13 cuts aggrecan, the water-holding molecule in cartilage, at two sites, one of them not seen with other enzymes. Purified MMP13 also...
They attack different parts of cartilage. MMP13 is the main enzyme that cuts type II collagen, the fibre network. ADAMTS5 is the main aggrecanase, cutting aggrecan, the...