Question

Both enzymes, kinase and phosphates are involved in the common covalent modification of proteins and phosphatase reverses the effect of kinase. However, the phosphorylation and dephosphorylation reactions are not reverse of each other. Explain in detail with focus on substrates and products of each reaction.

Answer 1

A kinase is an enzyme that attaches a phosphate group (PO43−) to a protein. A phosphatase is an enzyme that removes a phosphate group (PO43−) from a protein.

Phosphorylation involves the covalent modification of the hydroxyl group in a protein with a phosphate group through the nucleophilic attack of the alpha phosphate in ATP by the oxygen in the hydroxyl.

Dephosphorylation involves the removal of the phosphate group through a hydration reaction by the addition of a molecule of water and release of the original phosphate group, reinstating the hydroxyl.