This thesis focuses on the biosynthesis machinery of the neurotransmitter dopamine and its therapeutic potential in the treatment of Parkinson’s disease, a degenerative disorder caused by a deficiency in dopamine. Although L-DOPA is the current treatment for Parkinson’s disease, it can lead to adverse effects and eventually lose effectiveness. As an alternative approach to replenish dopamine levels, this thesis suggests regulating the activity of tyrosine hydroxylase, the rate-limiting enzyme involved in dopamine production. By stimulating tyrosine hydroxylase activity, dopamine production can be increased, activating dopamine cells in the brain. The activity of tyrosine hydroxylase is regulated by Ser40 phosphorylation, a chemical reaction in which a phosphate group is added to an amino acid in the enzyme. This thesis explores the mechanisms that influence Ser40 phosphorylation and how they can be manipulated to increase the dopamine biosynthesis machinery in the dopamine neurons that are affected in Parkinson’s disease, specifically. The research findings indicate that cyclic nucleotide-mediated signaling plays a vital role in promoting Ser40 phosphorylation. Furthermore, the thesis investigates the impact of inhibiting phosphodiesterases, which break down cyclic nucleotides, on Ser40 phosphorylation. The results demonstrate that phosphodiesterase inhibition can upregulate tyrosine hydroxylase Ser40 phosphorylation and, as such, can stimulate the dopamine biosynthesis machinery. Overall, these findings suggest that manipulating tyrosine hydroxylase activity through phosphodiesterase inhibition could be a promising strategy to replenish dopamine levels and improve the quality of life for Parkinson’s disease patients.