What is detected by the HVA metabolite, produced by the organic chemical of the catecholamine and phenethylamine families?
Homovanillic acid:  Homovanillic acid is used as a reagent to detect oxidative enzymes, and is associated with dopamine levels in the brain. Dopamine: Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is an organic chemical of the catecholamine and phenethylamine families that plays several important roles in the brain and body.
oxidative enzymes