Modulation of enzymatic activity of human mast cell tryptase and chymase by protease inhibitors.

AIM: To investigate the actions of protease inhibitors on the enzymatic activities of tryptase and chymase in similar experimental systems.
METHODS: Human lung tryptase and human skin chymase were purified by a similar procedure involving high salt extraction of tryptase, heparin agarose affinity chromatography, and S-200 Sephacryl gel filtration chromatography. Actions of protease inhibitors on tryptase and chymase activities were examined by enzyme assays.
RESULTS: The specific activities of tryptase and chymase were 2.1 kU/g protein and 4.9 kU/g protein, respectively. Both preparations showed a single diffuse band on SDS-PAGE. Among non-native protease inhibitors, N-(1-hydroxy-2-naphthoyl)-L- arginyl-L-prolinamide hydrochloride (HNAP), leupeptin, antipain, benzamidine, and protamine inhibited more than 90 % enzymatic activity of tryptase, whereas soy bean trypsin inhibitor (SBTI), Z-Ile-Glu-Pro-Phe-CO2Me (ZIGPPM) and chymostatin inhibited more than 95 % enzymatic activity of chymase. Native protease inhibitors alpha 1-antitrypsin and secretory leukocyte protease inhibitor (SLPI) inhibited more than 90 % enzymatic activity of chymase, but lactoferrin appeared to enhance chymase enzymatic activity. All the 3 inhibitors had weak inhibitory actions on tryptase.
CONCLUSION: The protease inhibitors tested had relatively good selectivity to either tryptase or chymase.