Amino Acid PKa Values
pKa values of amino acid side chains play an important role in defining the pH-dependent characteristics of a protein. The pH-dependence of the activity displayed by enzymes and the pH-dependence of protein stability, for example, are properties that are determined by the pKa values of amino acid side chains.
The pKa values of an amino acid side chain in solution is typically inferred from the pKa values of model compounds (compounds that are similar to the side chains of amino acids). (See Amino acid for the pKa values of all amino acid side chains inferred in such a way.) The table below lists the model pKa values that are normally used in a protein pKa calculation.
| Amino Acid | pKa |
|---|---|
| Asp (D) | 3.9 |
| Glu (E) | 4.3 |
| Arg (R) | 12.0 |
| Lys (K) | 10.5 |
| His (H) | 6.08 |
| Cys (C) | 8.28 (-SH) |
| Tyr (Y) | 10.1 |
Read more about this topic: Protein P Ka Calculations
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