The interaction of α2-macroglobulin with proteinases. Binding and inhibition of mammalian collagenases and other metal proteinases

Abstract

1. Experiments were performed to determine whether the specific collagenases and other metal proteinases are bound and inhibited by α2-macroglobulin, as are endopeptidases of other classes. 2. A specific collagenase from rabbit synovial cells was inhibited by human serum. The inhibition could be attributed entirely to α2-macroglobulin; α1-trypsin inhibitor was not inhibitory. α2-Macroglobulin presaturated with trypsin or cathepsin B1 did not inhibit collagenase, and pretreatment of α2-macroglobulin with collagenase prevented subsequent reaction with trypsin. The binding of collagenase by α2-macroglobulin was not reversible in gel chromatography. 3. The collagenolytic activity of several rheumatoid synovial fluids was completely inhibited by incubation of the fluids with α2-macroglobulin. 4. The collagenase of human polymorphonuclear-leucocyte granules showed time-dependent inhibition by α2-macroglobulin. 5. The collagenolytic metal proteinase of Crotalus atrox venom was inhibited by α2-macroglobulin. 6. The collagenase of Clostridium histolyticum was bound by α2-macroglobulin, and inhibited more strongly with respect to collagen than with respect to a peptide substrate. 7. Thermolysin, the metal proteinase of Bacillus thermoproteolyticus, was bound and inhibited by α2-macroglobulin. 8. It was shown by polyacrylamidegel electrophoresis of reduced α2-macroglobulin in the presence of sodium dodecyl sulphate that synovial-cell collagenase, clostridial collagenase and thermolysin cleave the quarter subunit of α2-macroglobulin near its mid-point, as do serine proteinases. 9. The results are discussed in relation to previous work, and it is concluded that the characteristics of interaction of the metal proteinases with α2-macroglobulin are the same as those of other proteinases.