Which enzymes are important in collagen degradation? How are they regulated?
The most important collagenolytic enzymes responsible for the cleavage of type I collagen belong to the matrix metalloproteinase (MMP) group. The collagenases are secreted in latent form and, when activated, cleave the collagen molecule at a single specific site following a glycine residue located about three quarters of the distance from the amino terminal end (between residues 775 and 776 of the α1[I] chain). Gelatinases and stromelysins then degrade the unfolded fragments.
Both α-macroglobulin and tissue inhibitors of metalloproteases (1 to 4) are capable of inhibiting collagenase activity. It is likely that other collagen types have type-specific collagenases capable of degrading them. Serum procollagen peptides, urinary hydroxyproline, urinary pyridinoline/deoxypyridinoline crosslinks, and serum C -telopeptides and urinary N -telopeptides are used as measures of collagen turnover.