The modified amino acid, called dihydroxyphenylalanine
(DOPA), has two functions.
TH is a key enzyme and serves as the rate-limiting enzyme in DA production, as it could convert dietary tyrosine to L- dihydroxyphenylalanine
(L-DOPA), which may in turn be converted by aromatic amino acid decarboxylase (AADC) to the production of DA.
Tyr is known to be the rate-limiting enzyme affecting the production of melanin pigment , which oxidates tyrosine to dihydroxyphenylalanine
(DOPA) and determines which type of melanin could be synthesized .
It's been known for a number of years that a key ingredient of mussel glue is dihydroxyphenylalanine
Catecholamines and dihydroxyphenylalanine
in metamorphosing larvae of the nudibranch Phestilla sibogae Bergh (Gastropoda: Opisthobranchia).
The bulk of the urinary dopamine may be from renal production and uptake of dopamine and decarboxylation of circulating dihydroxyphenylalanine
(dopa), [23, 24] which is in turn from hydrolysis of tyrosine.