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SummaryCollagen devoid of telopeptides has been prepared according to the method of Rubin. It has been shown that this partially degraded collagen has not lost the ability to adhere and to aggregate platelets.

1. An activator catalysing specifically conversion of latent forms of human leucocyte collagenase and gelatin-specific protease into the active forms, has been isolated from rheumatoid synovial fluid and purified 55-fold with a yield of 16%. 2. Molecular weight of the activator is about 35 000. 3. The activator is thermolabile, and is irreversibly inactivated at pH below 5.5 or in the presence of low concentrations of trypsin or papain; it is resistant to the action of lysozyme, hyaluronidase, diisopropylfluorophosphate, soybean trypsin inhibitor, p-chloromercuribenzoate, iodoacetamide and dithiothreitol. 4. The activator did not show any activity towards collagen, gelatin, casein, haemoglobin, histones, elastin or p-phenylazobenzyloxycarbonyl-peptide.

Production of a factor activating leucocyte procollagenase by tissue culture of rheumatoid synovium was shown. The activator was isolated, partly purified, and shown to be thermolabile, nondialysable, and had no activity toward casein, haemoglobin, histones, and PZ-peptide. The activity of the activator was partly decreased by trypsin.

Seven anti-inflammatory agents were tested for their possible inhibition of human leucocyte collagenase. Acetylsalicylic acid, indomethacin, phenylbutazone, sanocrisin and flufenamic acid were found to inhibit collagenase at concentrations which might be present in tissue during therapy. Hydrocortisone acetate and cyclophosphamide were ineffective.

A collagenase proenzyme was found in crude human leucocyte extract. An activating agent was present in all the ten studied rheumatoid synovial fluids taken from knee joints. The activator was found to be heat labile and nondialyzable. Activation occurred after mixing crude extract with synovial fluid (protein ratio 1:1) and heating the mixture for several hours at 37°C. Collagenase was produced from proenzyme both when the activator acted on the crude leucocyte extract and when it acted on the same extract previously devoid of free collagenase; however, activation did not occur in crude extracts partially purified with dioxan. The amount of proenzyme in the extract was about 3 times greater than that of free collagenase. Activated proenzyme was capable of releasing soluble hydroxyproline peptides from reconstituted collagen fibrils at 37°C, and of decreasing the viscosity of collagen in solution at 26°C. Both the activated proenzyme and the free collagenase from leucocytes produced the same degradation products from soluble native collagen. An alternative possibility, that the activator was present in crude extract and the proenzyme in synovial fluid, was experimentally ruled out. The role of collagenase proenzyme from leucocytes in the inflamatory state of tissues is discussed.