Discussion

Abstract

Four General issues dominated discussions concerning tryptophan hydroxylase (TpH) and pterin cofactor regulation in brain and adrenal: 1) the multiplicity of potential mechanistic meanings implicit in the Michaelis-Menten constants when used in multicomponent systems under non-saturated conditions; 2) the statedependence, variety of actions and attendant variability, the action of regulatory effectors, from ligands to reaction conditions; 3) the ambiguities remaining in the biosynthetic pathway, metabolic role, methods of measurement, appropriate regional and subcellular values, and the significance of neural systemactive drug actions on brain and adrenal tetrahydrobiopterin (BH₄); 4) features of the interaction between brain reduced pterin levels and activity state of the mixed function oxydases with respect to the characteristic quality of the regulation of amine synthesis.