H-Ala-Pro-AFC

A method for the localization of activities of proteases using substrates with 7-amino-3-trifluoromethylcoumarine (AFC) leaving group is described. 0.1 ml of 5-20 mMol solution of the respective substrate (Gly-Pro-AFC, Ala-Pro-AFC, Z-Ala-Arg-Arg-AFC, Z-Gly-Arg-Arg-AFC, Z-Gly-Gly-Arg-AFC, D-Val-Leu-Lys-AFC) in dimethylsulfoxide or dimethylformamide was added to 0.9 ml of 0.1 M Tris-HCl buffer, pH 7.4-7.8 or 0.1 M cacodylate buffer, pH 5-5.5. In the case of Z-Ala-Arg-Arg-AFC (cathepsin B substrate) 15 mM EDTA and 12 mM dithiothreitol were added. 7 mM amiloride or 2 mg/1 ml aprotinin were used as inhibitors with Z-Gly-Gly-Arg-AFC (urokinase substrate) and with D-Val-Leu-Lys-AFC (plasmin substrate). Substrate solutions were mixed with an equal amount of 2% agar solution in distilled water or in the respective buffer the pH of which was adjusted according to the pH optimum of the enzyme to be demonstrated. The agar solution was kept in a water bath at a temperature of 50-60 degrees C. After careful mixing, the substrate solution in agar was poured into a cylindrical vessel closed with a semipermeable membrane (Nephrophan) on which unfixed cryostat sections were mounted. 1-5 mM AFC solution in dimethylsulfoxide or dimethylformamide instead of the substrate was used as the control. Quenched samples of rat kidney and jejunum, biopsies of human jejunal mucosa, and of colorectal and uterine tumors were employed for the preparation of sections. After gelification of the medium in a refrigerator the vessels with sections were incubated in the dark at 37 degrees C for 0.5-several h. The reaction was controlled in a fluorescence microscope with an epiillumination adjusted to the FITC fluorescence and documented. A yellowish green fluorescence depicts sites where AFC was set free (sites with enzyme activity). When the reaction reached the required intensity the membranes were cut off, transferred to glass slides, mounted in glycerol, observed and photographed immediately (due to the solubility of AFC in glycerol). An acceptable cellular localization was achieved. The method with AFC substrates can be recommended for comparative biochemical and histochemical studies of proteases using the same substrate and for cases in which no other reliable procedure for the localization of the respective enzyme activity is available (e.g. urokinase, plasmin).

Probing attachment loss and radiographical measurements of bone loss were made on 20 untreated chronic periodontitis patients. At a second visit, gingival crevicular fluid was collected on filter paper strips from the deepest accessible interdental probing site of each tooth. Gingival crevicular fluid volumes were determined and the samples eluted into buffer. Protease activities in the resulting eluates were assayed with peptidyl derivatives of 7-amino-4-trifluoromethyl coumarin (AFC). Cathepsin B/L-like activity was determined with Bz-Val-Lys-Lys-Arg-AFC, elastase-like activity with MeOSuc-Ala-Ala-Pro-Val-AFC, tryptase-like activity with Z-Ala-Ala-Lys-AFC, trypsin-like activity with Z-Gly-Gly-Arg-AFC and dipeptidyl peptidase IV-like activity with Ala-Pro-AFC. Total enzyme activities and enzyme concentrations correlated positively with probing attachment loss and bone loss in linear regression analysis. This was true at both a patient level, using mean patient values, and a site level, using either individual patient or pooled patient data. All of these correlations were highly statistically significant for site comparisons. In inter- and intra-patient comparisons the proportion of significant correlations was greater for total enzyme activity than concentration. Clinical and radiological measurements of attachment loss showed generally similar levels of correlation. Total enzyme activities had good specificity and sensitivity as indicators of attachment loss in this cross-sectional study. The results support further investigation of the diagnostic potential of gingival crevicular fluid proteases in evaluation of the periodontal condition.

Crevicular fluid samples were collected from 20 gingivitis and periodontitis patients using filter paper strips; these were then eluted into buffer. Portions of each sample were combined and the activities of this pooled eluate against different peptidyl derivatives of 7-amino-4-trifluoromethyl coumarin (AFC) were examined with respect to their pH profiles and effector responses. Ca-thepsin B- and L-like activity was detected with Bz-Val-Lys-Lys-Arg-AFC; elastase-like activity with MeOSuc-Ala-Ala-Pro-Val-AFC; tryptase-like activity with Z-Ala-Ala-Lys-AFC; trypsin-like activity with Z-Gly-Gly-Arg-AFC; and dipeptidyl peptidase (DPP) IV-like activity with Ala-Pro-AFC. The selectivity and sensitivity of these assays were improved by choice of appropriate conditions. The cathepsin B- and L-, elastase-, tryptase-, and trypsin-like activities all had properties consistent with those from host sources, whilst partial inactivation of the DPP IV-like activity by heat treatment (60 degrees C for 30 min) suggested that it may have represented a mixture of human and Bacteroides gingivalis enzymes. Individual patient eluates showed wide variations in enzyme concentrations, but generally elastase-like activity was by far the highest. The sensitivity of the assays with AFC-linked substrates was such that it should prove possible to measure all five different types of activity in crevicular fluid samples from local periodontal disease sites.