TH

Tyrosine Hydroxylase (TH), also termed DYT5b or TH, is the rate-limiting enzyme in catecholamine biosynthesis, catalyzing tyrosine hydroxylation to L-DOPA, the precursor for dopamine, norepinephrine, and epinephrine. Encoded by the TH gene (chromosome 11p15.5), TH activity is regulated by phosphorylation at serine residues (e.g., Ser8, Ser19) and feedback inhibition by catecholamines, modulating dopamine homeostasis in dopaminergic neurons and adrenal medulla . Dysregulation of TH causes severe neurological disorders, including Segawa syndrome (autosomal recessive TH deficiency) and Parkinson’s disease, characterized by motor deficits, rigidity, and tremors due to dopamine depletion .
Drug development for TH-related disorders focuses on dopamine replacement (e.g., L-DOPA) and enzyme modulation. Small-molecule activators like N-methyl-N’-(2-pyridinylmethyl)-1,2-dihydro-3H-indol-3-one derivatives enhance TH stability and activity in preclinical models. Gene therapy approaches, such as AAV-mediated TH overexpression, aim to restore dopamine synthesis in genetic deficiencies. Challenges include achieving brain-penetrant delivery and minimizing peripheral side effects like hypertension from excessive catecholamine production .