Temperature on Enzymes

The total free energy of stabilization for proteins is, even at the temperature of maximum stability, quite small. For the majority of proteins 

The Arrhenius equation describes temperature dependence of the rate constant of a chemical reaction  

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FIGURE 14.12 The effect of temperature on enzyme activity. The relative activity of an enzymatic reaction as a fnncdon of tempera-tnre. The decrease in the activity above 50 C is dne to thermal denatnradon. 

Cloughley, J. B., The effect of temperature on enzyme activity during the fermentation phase of black tea manufacture. J. Sci. Food Agri., 31 920, 1980. 

Figure 8.1 The effect of temperature on enzyme-catalysed reactions. The velocity of a chemical reaction increases with increasing temperature (A) but because of the increasing denaturation of the protein, the proportion of active enzyme falls (B). These two processes result in the characteristic temperature profile of an enzyme (C).

There are three distinct findings for the effect of temperature on enzyme activity and stability in carbon dioxide. The first is that as temperature increases, activity of the enzyme decreases. Nakamura et al. (1986), Chi et al. (1988), and Lee et al. (1993) all observed slight decreases in activity as temperature was increased slightly. Chulalaksananukul et al. (1993) observed a more marked decrease in activity and attribute the loss of activity to thermal denaturation of the enzyme. 

Understand the effects of pH, ionic strength, and temperature on enzyme reactions. 

Keeling, P. L., Banisadr, R., Barone, L., Wasserman, B. P., and Singletary, G. W. 1994. Effects of temperature on enzymes in the pathway of starch biosynthesis in developing wheat and maize grain. Aust. J. Plant Physiol 21, 807-827. 

The effect of temperature on enzyme immunoassays should not be overlooked, and adequate thermo-static control is mandatory. This problem is not met with in other optical immunoassays which gives the latter some advantages. 

The pH of the desizing bath is maintained by adding acid or alkali. The effects of pH and temperature on enzyme activity are shown in Figs. 3-3 and 3-4 respectively. However storing the enzyme at a fixed temperature shows that the activity steadily decreases with time (Fig. 3-5). In general, changes in pH, tem-... 

Thus it is quite evident that exogenous proteolytic enzymes alter the functionality of meat proteins, i.e. increase tenderness, by a more or less random attack on the various muscle proteins. However, this alteration occurs primarily during the cooking period because of denaturation of substrate proteins and the effects of increased temperature on enzyme activity. 

Fig. 3.13 Schematic representation of the effect of temperature on enzyme activity and stability...

The effect of temperature on enzyme reactivity (expressed by the rate constant kcat or the parameter V) can be analyzed from the theory of the activated complex (or transition state theory, TST) or else by using the semi-empirical correlation of Arrhenius. According to TST (Rooney 1995), the equation of Eyring describes the effect of temperature on any rate constant ... 

There are a number of useful reviews of the effects of temperature on enzyme activity, and these apply as much to reactions at 100° as at 37°. However, enzymes stable at 100° have a number of advantages as research subjects. For example, they can be used to investigate enzymes that are particularly unstable when isolated from mesophiles, to slow reactions without the use of cryosolvents, and to probe the effect of temperature on enzyme and protein behavior over a very wide temperature range. They can also be used to study enzyme behavior under conditions that would denature most enzymes, since enzymes resistant to heat are also, at room temperature, resistant to organic solvents, chaotropic agents, and proteolysis. Clearly, such stable enzymes also have a variety of applications in biotechnology, where protein stability may be an important practical and economic factor. 

Figure 10.7 The effect of temperature on enzyme-catalyzed reaction rates.

Effect of Temperature on Enzyme I Association. Reproduced from ref. 7. 

Fig 2 Effect of temperature on enzyme activity. Assay conditions as reported in Table... 

Indrawati, I., Smout, C., and Hendrickx, M. (2003) Efiects of comhmed pressure and temperature on enzymes related to quality of fruits and vegetables from kinetic information to process engineering aspects. Critical Reviews in Food Science and Nutrition,... 

Sizer, Irwin W., Effects of Temperature on Enzyme Kinetics... HI 35... 

The graph shows the effect of temperature on enzyme activity. Explain why the graph has the general shape shown. For human enzymes, at what temperature would you expect the maximum in the curve to appear ... 

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