LAUSR

Abstract The aim of this work was to investigate the effects of pH and temperature on the structural characteristics of the Pediococcus pentosaceus R1 protease, which was isolated from Harbin dry sausage. UV-vis, fluorescence, circular dichroism and Fourier transform infrared spectroscopy were used to evaluate the structural changes as a function of pH and temperature. The protease had a stable spatial structure at pH 5 and 30 °C, and the extended secondary structures of the protease were identified. The structure of protease was changed at pH 8 and 70 °C, with changes predominantly manifested as changes in secondary structure components, the α-helices, β-sheets, β-turns and random coils contents at pH 8 were 5.32%, 37.08%, 19.45% and 38.22%, respectively; and at 70 °C the contents were 5.47%, 40.62%, 19.56% and 34.35% respectively, which were significantly different from that at pH 5, 30 °C. Carbonyl vibration (1651 cm-1), –NH vibration (1540 cm-1), C–H stretching vibration (2959-2857 cm-1) and disulfide bonds (560-460 cm-1)were identified in P. pentosaceus R1 protease under various pH and temperature conditions. Molecular docking showed that the protease can interact with actin and myoglobin, which indicates certain options for the application of this enzyme in the fermentation of Harbin dry sausage.