Bovine mast cell tryptase inactivation: effect of temperature.

The thermal stability of bovine tryptase, a serine proteinase present in the bovine mast cell secretory granules, has been studied by circular dichroism and catalytic activity measurements. Bovine tryptase shows a peculiar dichroic negative band centered at 230 nm. The decrease of this band in a temperature dependent fashion represents a good marker to monitor the native conformation of the enzyme. Bovine tryptase inactivation has been followed in the temperature range between 10 degrees C and 80 degrees C, and reversibility of the process has been also studied. The results obtained show that the temperature dependent loss of activity and the conformational change, as monitored by circular dichroism, are both fully reversible between 10 degrees C and 40 degrees C, while only the CD change displays reversibility in going from 60 degrees C to 10 degrees C. Moreover, a functional analysis of the temperature-dependent enzymatic activity of bovine tryptase toward peptide substrates in the 10 degrees C - 40 degrees C range is reported and compared with the temperature dependence of the enzymatic activity of trypsin.