Question

The activity of many enzymes is regulated by reversible covalent modifications. Kinases add a phosphate group from an ATP to a specific hydroxyl group on an amino acid residue within an enzyme. Which of the following amino acids can be phosphorylated by a kinase? (Select all that apply) Cys His Tyr Thr Phe Ser Val

Answer 1

Phosphorylation can be seen in Serine, threonine and tyrosine amino acids via phospoEster bond formation.

Histidine also shows phosporylation via phosporamidate bond formation.

Answer 2

The amino acids that can be phosphorylated by a kinase are:

1. Ser (Serine)

2. Thr (Threonine)

3. Tyr (Tyrosine)

4. His (Histidine)

These amino acids possess hydroxyl (OH) groups on their side chains, which can act as the target for phosphorylation by kinases. Cys (Cysteine), Phe (Phenylalanine), and Val (Valine) do not have hydroxyl groups on their side chains and therefore cannot be phosphorylated by kinases.