3,4-Dihydroxyphenylacetic acid

3,4-Dihydroxyphenylacetic acid is a metabolite of the neurotransmitter dopamine. Dopamine can be metabolized into one of three substances. One such substance is DOPAC. Another is 3-methoxytyramine. Both of these substances are degraded to form homovanillic acid. Both degradations involve the enzymes monoamine oxidase and catechol-O-methyl transferase, albeit in reverse order: MAO catalyzes dopamine to DOPAC, and COMT catalyzes DOPAC to HVA; whereas COMT catalyzes dopamine to 3-MT and MAO catalyzes 3-MT to HVA. The third metabolic end-product of dopamine is norepinephrine.
[Image:Dopamine degradation.svg|thumb|left|400px|class=skin-invert-image|Biodegradation of dopamine]
It can also be found in the bark of Eucalyptus globulus.
This product has been synthesized from 4-hydroxyphenylacetic acid via aerobic biotransformation using whole cell cultures of Arthrobacter protophormiae.