Thermal stability pepsins

Thermal Stability. The temperature optimum for arctic cod pepsin is approximately 32°C see Table III) and the enzyme is unstable when incubated at temperatures above 37°C see Figure 4) in contrast to porcine pepsin which has a temperature optimum of approximately 47°C and is unstable at temperatures above 50°C see Figure 4). Accordingly, there is a difference in thermal stability of approximately 13°C for the two enzymes. Similar differences in temperature optima were observed when Greenland cod and American smelt were compared with PP see Table III). These data are consistent with previous reports for intracellular enzymes and for crude preparations of pyloric caeca enzymes from other low-temperature-adapted organisms (42). 

Figure 4. Thermal stability of arctic cod pepsin and porcine pepsin. Enzymes were incubated at pH 1.9 without substrate for 1 h and subsequently assayed at 30°C arctic cod (%) pig ( ).

The present study indicates that the extracellular enzyme, pepsin, exhibits striking differences from its mammalian homologue with respect to optimum pH, Ea for catalysis, thermal stability, and substrate affinity. These data are interesting from the viewpoint of biological adaption at low temperatures, but they also provide some substance to our contention that enzymes from fish plant wastes can have sufficiently unique properties to justify their use over conventional sources of enzymes used as food-processing aids. The relatively low Eas for protein hydrolysis by fish pepsins indicate they may be especially useful for protein modifications at low temperatures. Alternatively, the poor thermal stability of the fish pepsins studied indicate that the enzymes can be inactivated by relatively mild blanching temperatures. The reality of this concept will have to await studies where the pepsins are used as food-processing aids. Such studies are currently underway in our laboratory. 

As indicated, this paper will concentrate mainly on questions related to stability of enzyme inhibitor proteins and lectins. In particular, differential scanning calorimetric findings on effects of specific interactions on thermal stability will be reviewed. Stabilities of these proteins to other denaturing agents are not considered here. Older work showed that proteinase inhibitors are generally highly stable some resist denaturation at 100 C when dry or in neutral or weakly acidic solutions. Some even survive the action of pepsin, and can thus reach the small intestine intact. 

The present paper summarizes the current knowledge of activating and stabilizing effect of AP ions on gastrointestinal fluids, especially on main gastrointestinal enzyme - pepsin. Therefore, there is a lack of information about thermal stability of pepsin in a presence of AP ions. As the binding mechanism of AP ions on pepsin is not still clear the objective of this study is to investigate the in vitro conditions the influence of different concentrations of... 

AP+ ions, physiological and toxic ones, on pepsin conformational stability during the process of thermal unfolding, with a purpose of better understanding of pepsin/aluminium interaction. 

Thermal stability of pepsin in a presence of Al ions followed by differential scanning calorimetry... 

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