Lysine is least soluble in water in the $\mathrm{pH}$ range
Lysine is least soluble in water in the $\mathrm{pH}$ range
3 to 4
5 to 6
6 to 7
9 to 10
Solution
An amino acid has lowest solubility at its isoelectric point $(\mathrm{pH}$ at which the amino acid carries no charge) and the isoelectric point of lysine is 9.7.