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. 1991 Aug 15;278(Pt 1):143–147. doi: 10.1042/bj2780143

Link protein as a monitor in situ of endogenous proteolysis in adult human articular cartilage.

Q Nguyen 1, J Liu 1, P J Roughley 1, J S Mort 1
PMCID: PMC1151460  PMID: 1883326

Abstract

The link protein components of proteoglycan aggregates in adult human articular cartilage show heterogeneity due to proteolysis. Cleavages near the N-terminus of the intact link proteins, before residues 17, 19 and 24, generate three proteins of slightly diminished size (LP3). Cleavages within the N-terminal disulphide-bonded loop, before residues 66 and 73 of the intact link proteins, generate proteins that yield smaller degradation products upon reduction (LP fragments). In vitro, modified link protein components of a similar size to LP3 can be generated by a variety of proteinases, but of the physiologically relevant enzymes only stromelysin, cathepsin B and cathepsin G have the ability to yield modified link proteins with N-termini identical with those observed in situ. None of the proteolytic agents tested was able to produce LP fragments with N-termini identical with those observed in situ, and the majority of proteinases were not able to cleave within the disulphide-bonded loops. Cathepsin L and hydroxyl radicals can cleave within the N-terminal disulphide-bonded loop, and have the potential of initially opening the loop to allow further proteolytic processing by other agents to generate the native cleavage sites.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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