A possible feed-back mechanism controlling the biosynthesis of 5-hydroxytryptamine

Abstract The effect of 5-hydroxytryptamine on the decarboxylation of 5-hydroxytryptophan by partially purified guinea pig l -aromatic amino acid decarboxylase was studied. 5-Hydroxytryptamine was found to inhibit the enzyme. The degree of inhibition was related to the time of preincubation of enzyme and 5-hydroxytryptamine and to the concentration of added pyridoxal phosphate, the co-factor for decarboxylation of 5-hydroxytryptophan. The possibility of a feed-back mechanism regulating the metabolism of 5-hydroxytryptamine is considered.