Final answer:
Phosphodiesterase (PDE) is the enzyme that deactivates cGMP by converting it into GMP, which ends the signal transduction pathway it is involved in.
Step-by-step explanation:
The enzyme responsible for the metabolic deactivation of TGMP, which is likely a typo for cGMP (cyclic guanosine monophosphate), is phosphodiesterase (PDE). This cytosolic enzyme deactivates and degrades cGMP by converting it into GMP, thus terminating the signaling cascade. In general, phosphodiesterase enzymes have a broader role in cellular regulation by degrading cyclic nucleotides, like cAMP and cGMP, which are secondary messengers in numerous signal transduction pathways. By decreasing cellular concentrations of these cyclic nucleotides, PDEs help revert cells back to their basal state after a signaling event has occurred.