Background：TH（Tyrosine 3-monooxygenase） converts L-tyrosine to L-3,4-dihydroxyphenylalanine （L-DOPA）,the essential and rate-limiting step to formation of dopamine and other catecholamines. TH plays an important role in the physiology of adrenergic neurons and can be used as a marker for dopaminergic and noradrenergic neurons.
