Characterization of helical cleavages in type II collagen generated by matrixins.

Several vertebrate collagenases have been reported to cleave type II collagen, leading to irreversible tissue destruction in osteoarthritis. We have investigated the action of MMP-1 and MMP-13 on type II collagen by use of neoepitope antibodies and N-terminal sequencing. Previous studies have suggested that the initial cleavage of type II collagen by MMP-13 is followed by a second cleavage, three amino acids carboxy-terminal to the primary cleavage site. We show here that this cleavage is also produced by APMA-activated MMP-1 in combination with MMP-3 (i.e. fully activated MMP-1). The use of a selective inhibitor of MMP-3 has shown that it is this enzyme, rather than interstitial collagenase which had been exposed to MMP-3, which makes the second cleavage. In addition we have identified, through N-terminal sequencing, a third cleavage site, three residues carboxy-terminal to the secondary site. Since MMP-2 is thought to be responsible for gelatinolytic action on type II collagen we have investigated the effect of MMP-2 after the initial helical cleavage made by either MMP-1 or MMP-13. A combination of MMPs-1, -2 and -3 results in both the second and third cleavage sites; adding MMP-2 to MMP-13 did not alter the cleavage pattern produced by MMP-13 on its own. We conclude that none of the three cleavage sites will provide information about the specific identity of the collagenolytic enzymes involved in collagen cleavage in situ. Staining of cartilage sections of osteoarthritis patients with the neoepitope antibodies revealed type II collagen degradation starting at or near the articular surface and extending into the mid and deep zones with increasing degeneration of the cartilage.

Kinetic constants for the hydrolysis of aggrecan by the papaya proteinases and their relevance for chemonucleolysis.

The four known proteinases from papaya latex, namely papain (EC 3.4.22.2), chymopapain (EC 3.4.22.6), caricain (EC 3.4.22.30), and glycyl endopeptidase (EC 3.4.22.25), were purified to homogeneity and fully characterized by single radial immunodiffusion and active-site titration. A modified HPLC gel permeation assay was used to determine the kinetic constants for aggrecan hydrolysis by the papaya proteinases. The disappearance of intact aggrecan monomer was first-order, indicating that for the four enzymes studied the Km was much larger than 0.5 microM and that kcat/Km = 1.2 +/- 0.1 x 10(6) M-1 s-1 for chymopapain, 1.20 +/- 0.08 x 10(6) M-1 s-1 for caricain, 0.90 +/- 0.02 x 10(6) M-1 s-1 for papain, and 0.120 +/- 0.005 x 10(6) M-1 s-1 for glycyl endopeptidase. Chymodiactin, the chymopapain preparation used for chemonucleolysis, consists of a mixture of chymopapain (70%), caricain (20%), and glycyl endopeptidase (4%). The rate constant for the aggrecan hydrolysis by such a mixture was not significantly different from the rate constant for pure chymopapain. As a result of these observations, we predict that pure chymopapain could replace partially purified chymopapain preparations for chemonucleolysis.

Fractionation and purification of the thiol proteinases from papaya latex.

Three cysteine proteinases, i.e. chymopapain, papaya proteinase IV and proteinase III, were purified to homogeneity from papaya latex using a combination of ion-exchange chromatography and hydrophobic interaction chromatography. During the purification procedure, the thiol-groups of the active center were reversibly blocked as mixed disulfides with 2-thiopyridone. Homogeneity was proved electrophoretically by native polyacrylamide gel electrophoresis (PAGE), sodium dodecyl sulfate (SDS)-PAGE and rechromatography on a Mono S 5/5 column at pH 5.0.