the Structural Stability andCatalytic Activity of Pepsin

Pepsin enzyme is synthesized in the gastric mucosa of vertebrates. Pepsin is composed of 327 amino acid residues، has a calculated molecular mass of 34KD. The structure is predominantly β-strand and random coil with limited α-helix. The two domains are connected via a six-stranded β-sheet plate. In this study used UV-Vis spectrophotometer pharmacia-4000 with electronic temperature controller system. Thermal stability of porcine pepsin has been investigated in the presence of organic solvents include butanol، ethanol، 1،4-Butanediol and glycerol in different concentrations (0-50% V/V) at pH=2. Tm of pepsin was decreased respective in the presence of butanol، ethanol، 1،4-Butanediol and Tm of pepsin increased in the presence of glycerol. Also we were studied the effects of these organic solvents on the activity of porcine pepsin. Activity of pepsin decreased respective in aqueous butanol، ethanol and 1،4-Butanediol with increasing organic solvent concentration and activity of pepsin increased in presence of glycerol with increasing organic solvent concentration. The changes caused in the catalytic activity by the water-miscible organic solvents include butanol، ethanol and 1،4-Butanediol may be related to structural changes، which were followed by means of thermal stability changes and also change in active site of pepsin. Glycerol stabilized structure of pepsin.