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. 2010 Sep;78(12):2699-706.
doi: 10.1002/prot.22786.

On the pH-optimum of activity and stability of proteins

Kemper Talley  1 , Emil Alexov
Affiliations

On the pH-optimum of activity and stability of proteins

Kemper Talley et al. Proteins. 2010 Sep.

Abstract

Biological macromolecules evolved to perform their function in specific cellular environment (subcellular compartments or tissues); therefore, they should be adapted to the biophysical characteristics of the corresponding environment, one of them being the characteristic pH. Many macromolecular properties are pH dependent, such as activity and stability. However, only activity is biologically important, while stability may not be crucial for the corresponding reaction. Here, we show that the pH-optimum of activity (the pH of maximal activity) is correlated with the pH-optimum of stability (the pH of maximal stability) on a set of 310 proteins with available experimental data. We speculate that such a correlation is needed to allow the corresponding macromolecules to tolerate small pH fluctuations that are inevitable with cellular function. Our findings rationalize the efforts of correlating the pH of maximal stability and the characteristic pH of subcellular compartments, as only pH of activity is subject of evolutionary pressure. In addition, our analysis confirmed the previous observation that pH-optimum of activity and stability are not correlated with the isoelectric point, pI, or with the optimal temperature.

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Figures

Fig. 1
Fig. 1
The average (averaged over the experimentally reported pH interval) pH-optimum of activity and the average pH-optimum of stability over 310 proteins (see Table 1 for details): (a) The pH-optimum of activity plotted against pH-optimum of stability. The correlation coefficient and the parameters of the fitting line are provided within the plot. (b) The distribution of the differences between the corresponding average pH-optima.
Fig. 2
Fig. 2
The average pH-optimum and the corresponding best fit pH-optimum. (a) The best fit pH-optimum of stability plotted against the corresponding average pH-optimum of activity. Correlation coefficient and the parameters of the fitting line are provided within the graph. (b) The distribution of the difference between the best fit pH-optimum of stability plotted against the corresponding average pH-optimum of activity. (c) The best fit pH-optimum of activity plotted against the corresponding average pH-optimum of stability. Correlation coefficient and the parameters of the fitting line are provided within the graph. (d) The distribution of the difference between the best fit pH-optimum of activity plotted against the corresponding average pH-optimum of stability.
Fig. 3
Fig. 3
The distribution of ΔpH-optimum(intervals).
See this image and copyright information in PMC

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