pKa Values of Ionizable Groups in Proteins Used for the Estimation of pI
| Terminal carboxyl | 3.1 |
| Aspartic and glutamic acid | 4.4 |
| Histidine | 6.5 |
| Terminal amino | 8.0 |
| Cysteine | 8.5 |
| Tyrosine or lysine | 10.0 |
| Arginine | 12.0 |
[i] The values were taken from Stryer (1995).