Recognition and catabolism of synthetic heterotrimeric collagen peptides by matrix metalloproteinases

Background: The general consensus is that interstitial collagens are digest ed by collagenases and denatured collagen by gelatinases, although processi ng of fibrillar and acetic-acid-soluble collagen by gelatinase A has also b een reported. One of the main difficulties in studying the mechanism of act ion of these matrix metalloproteinases (MMPs) derives from the physicochemi cal properties of the natural triple-helical collagen, which makes ii diffi cult to handle. Results: Synthetic heterotrimeric collagenous peptides that contain the col lagenase cleavage site of human collagen type I and differ in the thermal s tability of the triple-helical fold were used to mimic natural collagen and gelatin, respectively. Results from digestion of these substrates by fibro blast and neutrophil collagenases (MMP-1 and MMP-8), as well as by gelatina se A (MMP-2), confirmed that the two classes of enzymes operate within the context of strong conformational dependency of the substrates. It was also found that gelatinases and collagenases exhibit two distinct proteolytic me chanisms: gelatinase digests the gelatin-like heterotrimer rapidly in indiv idual steps with intermediate releases of partially processed substrate int o the medium, whereas collagenases degrade the triple-helical heterotrimer by trapping it until scission through all three alpha chains is achieved. Conclusions: The results confirm the usefulness of synthetic heterotrimeric collagenous peptides in the folded and unfolded state as mimics of the nat ural substrates collagen and gelatin, respectively, to gain a better a insi ght into the proteolytic mechanisms of matrix metalloproteinases.