Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the synthesis of the neurotransmitter dopamine and other catecholamines. TH functions as a tetramer, with each subunit composed of a regulatory and catalytic domain, and exists in several different isoforms. This enzyme is required for embryonic development since TH knockout mice die before or at birth. Plays an important role in the physiology of adrenergic neurons (By similarity). Positively regulates the regression of retinal hyaloid vessels during postnatal development (By similarity).
