an amino acid, C 9 H 11 NO 4 , formed from tyrosine in the liver during melanin and epinephrine biosynthesis: the L-dopa isomer is converted in the brain to dopamine.
Biochemistry. a catecholamine neurotransmitter in the central nervous system, retina, and sympathetic ganglia, acting within the brain to help regulate movement and emotion: its depletion may cause Parkinson's disease. Compare dopa.
