TH

Source: NCBI Gene, accessed 2026-10-07.

Protein

Tyrosine 3-monooxygenase

Function

Catalyzes the conversion of L-tyrosine to L-dihydroxyphenylalanine (L-Dopa), the rate-limiting step in the biosynthesis of catecholamines, dopamine, noradrenaline, and adrenaline. Uses tetrahydrobiopterin and molecular oxygen to convert tyrosine to L-Dopa. In addition to tyrosine, is able to catalyze the hydroxylation of phenylalanine and tryptophan with lower specificity (By similarity). Positively regulates the regression of retinal hyaloid vessels during postnatal development (By similarity).

Pathway

Catecholamine biosynthesis; dopamine biosynthesis; dopamine from L-tyrosine: step 1/2.

Subcellular location

Cytoplasm, perinuclear region; Nucleus; Cell projection, axon; Cytoplasm; Cytoplasmic vesicle, secretory vesicle, synaptic vesicle.

Tissue specificity

Mainly expressed in the brain and adrenal glands.

Associated conditions

Segawa syndrome autosomal recessive (ARSEGS).

Source: UniProtKB/Swiss-Prot P07101, release 2026_03, licensed CC BY 4.0. This is the protein’s normal biology, not evidence about post-drug syndromes; associated conditions are inherited disorders of the gene, not PFS, PSSD or PRSD.

Written for the whole neurotransmission family, not for TH specifically.