This 1996 study found that cartilage cells (chondrocytes) in worn human cartilage make MMP13. In the lab, MMP13 cut type II collagen into the classic three-quarter and one-quarter pieces, and it turned type II collagen over at least ten times faster than MMP-1, the collagenase researchers had suspected until then.
The team looked for collagenase-3 in human cartilage from people with osteoarthritis, using three methods: a PCR search for its genetic message, Northern blots, and antibodies that detect the protein directly. They tested whether interleukin-1 alpha, an inflammatory signal, changed MMP13 and MMP-1 levels in the cartilage. They also made recombinant MMP13 and set it against intact type II collagen and a synthetic peptide to see where, and how fast, it cut.
Chondrocytes in the cartilage made MMP13. Levels of MMP13 and MMP-1 varied, and interleukin-1 alpha raised both significantly, as genetic message and as protein. MMP13 cut type II collagen into characteristic three-quarter and one-quarter fragments at the same bond MMP-1 cuts, then made a second cut that trimmed three amino acids from the end of the shorter piece. It turned over type II collagen at least ten times faster than MMP-1.
The cartilage came from people with osteoarthritis, and the abstract does not give the number of donors or compare it with healthy cartilage. The speed comparison was made with purified enzymes in the lab, not inside a living joint where inhibitors and other enzymes are also at work. It shows MMP13 can cut type II collagen fast. It does not measure how much of the collagen loss in a real joint is down to MMP13.
Before this paper, MMP-1 was the main collagenase suspect in cartilage. The tenfold speed difference on type II collagen, the cartilage collagen, is the main reason researchers turned their attention to MMP13. The authors concluded the enzyme plays a significant role in cartilage collagen breakdown and has to be part of any plan to block collagenases.
MMP13, short for matrix metalloproteinase-13 and also called collagenase-3, is an enzyme that cuts collagen. Cartilage cells make it, and of the collagen-cutting enzymes...
Both are collagenases, enzymes that can cut intact collagen, and they cut type II collagen at the same bond. MMP13 is much faster at it: at least ten times faster than...
MMP13 cuts type II collagen, the rope-like fibre that gives cartilage its strength. It cleaves each three-stranded collagen molecule at one spot, leaving a three-quarter...