Tyrosine Hydroxylase (TH) is encoded by the gene mapped to human chromosome 11p15.5, close to the insulin (INS) and Harvey-ras-1 (HRAS) genes. The N-terminal end of the protein plays a vital role in maintaining intracellular stability of the enzyme. tyrosine hydroxylase is expressed in various tissues such as brain, adrenal medulla and sympathetically innervated tissues. The enzyme is characterized with a regulatory domain (R), a catalytic domain (C) at N-terminal end, and a coiled-coil domain at the C-terminal end.
Tyrosine Hydroxylase (TH) specifically catalyzes the hydroxylation of the amino acid L-tyrosine to 3, 4-dihydroxy-L-phenylalanine (L-DOPA). TH is a rate-limiting enzyme involved in the synthesis of catecholamine, involved in several brain functions, such as attention, memory, cognition, and emotion. Phosphorylation of the N-terminal portion of tyrosine hydroxylase controls the degradation of this enzyme by the ubiquitin-proteasome pathway. Alteration in the expression of the gene results in the pathogenesis of Parkinson′s disease (PD). Point mutation in the gene coding for TH leads to Segawa′s syndrome.
