How does phosphorylation result in the modification of an enzyme to either increase or decrease its activity?

• A. Phosphorylation causes structural changes by adding a phosphate group to the enzyme.
• B. Phosphorylation blocks the active site of the enzyme by adding a phosphate group to the enzyme.
• C. Phosphorylation cleaves specific peptide bonds in the enzyme.
• D. Phosphorylation alters enzyme activity by adding a hydroxyl group to it.

Answer: (A)