Final answer:
cAMP is hydrolyzed by phosphodiesterase, which is the enzyme that converts cAMP into AMP, thereby terminating its signaling function in the cell.
Step-by-step explanation:
The question asks which enzyme is responsible for hydrolyzing cyclic AMP (cAMP) in the cell. The correct answer is E. Phosphodiesterase. This enzyme converts cAMP into AMP, thus terminating the signal that cAMP carries within the cell. The function of cAMP is to serve as a second messenger, particularly by binding to and activating cAMP-dependent kinase, also known as A-kinase. A-kinase plays a crucial role in various metabolic pathways through the phosphorylation of proteins, which results in their activation.
Other enzymes mentioned in the question, such as protein kinase A and phosphatases, have different roles. Protein kinase A is the kinase that is activated by cAMP, while phosphatases remove phosphate groups from proteins, which is the opposite of what kinases do. Hence, phosphodiesterase is the enzyme that performs the specific function of degrading cAMP, not the others listed.