Answer:
A. Protein phosphatase I
Step-by-step explanation:
Protein kinase A (PKA) is an enzyme that phosphorylates proteins by transferring a phosphate group from ATP to a specific amino acid residue, usually serine or threonine. This process can alter the activity, localization, or interactions of the target protein. To reverse the effects of PKA, a phosphatase enzyme is needed to remove the phosphate group from the protein. One example of such an enzyme is protein phosphatase I (PPI), which can dephosphorylate many substrates of PKA, such as glycogen synthase and glycogen phosphorylase. Therefore, the answer to your question is A. Protein phosphatase.