“… L-tryptophan , tetrahydropteridine:oxygen oxidoreductase [5-hydroxylating]; EC 1.14.16.4; TPH), the initial …-limiting enzyme in the biosynthesis of the neurotransmitter serotonin, was inhibited directly by benserazide , an inhibitor of aromatic-L-amino-acid decarboxylase (3,4-…-L-phenylalanine carboxy-lyase; EC 4.1.1.28; AAAD).”