Answer: tyrosine

AnswerCrossword Clue
tyrosinea phenolic amino acid C9H11NO3 that is a precursor of several important substances (as epinephrine and melanin)
tyrosinecrystalline amino acid, HOC6H4CH2CH(NH2)COOH, abundant in ripe cheese, that acts as a precursor of norepinephrine and dopamine. Symbol: Y