Interaction of β₁‐Anticollagenase from Human Plasma with Collagenases from Various Tissues and Competition with α₂‐Macroglobulin

β 1 ‐Anticollagenase from human plasma forms an inactive enzyme‐inhibitor complex with active human polymorphonuclear leukocyte collagenase [Macartney, H. W. and Tschesche, H. (1983) Eur. J. Biochem. 130 , 85–92]. The inhibitor was shown to contain a reactive sulfhydryl group necessary for inhibition of the collagenase. Inhibition of the enzyme by β 1 ‐anticollagenase was shown to take place via a thiol/disulfide interchange reaction similar to the mechanism reported for the reaction between polymorphonuclear leukocyte collagenase and the polymorphonuclear collagenase inhibitor [Macartney, H. W. and Tschesche, H. (1980) FEBS Lett. 119 , 327–332]. The observations made in this paper have shown that the collagenases obtained from other human tissues, such as rheumatoid synovial fluid, embryonic skin fibroblasts, diabetic skin fibroblasts and normal skin fibroblasts, all react with β 1 ‐anticollagenase via a thiol/disulfide interchange mechanism, and are inhibited in a 1:1 stoichiometric reaction. Reaction of the inhibitor with the collagenases can be blocked by alkylation of the inhibitor's free sulfhydryl group with iodoacetamide, or by reaction of the inhibitor with disulfide‐containing compounds such as cystine, oxidised glutathione, insulin, relaxin or trypsinogen. The β 1 ‐anticollagenase–collagenase complexes (latent enzyme) can all be reactivated with disulfide‐containing compounds, such as those mentioned above. An activation process has been reported for human latent polymorphonuclear leukocyte collagenase via a thiol/disulfide interchange as catalysed by the glutathione cycle in a peroxidase‐coupled reaction to glucose metabolism [Tschesche, H. and Macartney, H. W. (1981) Eur. J. Biochem. 120 , 183–190]. The same physiological activation process is capable of reactivating β 1 ‐anticollagenase–collagenase complexes in a reversible manner. It was further shown in competition experiments with β 1 ‐anticollagenase (and with human leukocyte collagenase inhibitor) and α 2 ‐macroglobulin that vertebrate collagenases were preferentially inhibited by the low‐molecular‐weight inhibitors. It could also be shown that there was no transfer of the enzyme to α 2 ‐macroglobulin from either β 1 ‐anticollagenase–collagenase, or leukocyte inhibitor–collagenase complexes indicating a true inhibitory function for the β 1 ‐anticollagenase and the leukocyte collagenase inhibitor.