The Aromatic Amino Acid Hydroxylases

Clozapine-induced dopamine release in the medial prefrontal cortex is augmented by a moderate concentration of locally administered tyrosine but attenuated by high tyrosine concentrations or by tyrosine depletion

“…Whether activated TH is less sensitive to inhibition by tyrosine is not known. Activation does, however, reduce the enzyme's susceptibility to end product inhibition (Joh et al 1978;Fujisawa and Okuno 1987), activating that TH which was previously suppressed by normally inhibiting levels of DA (Kumer and Vrana 1996;Fitzpatrick 1998). Increased tyrosine hydroxylation by antipsychotic drug-activated TH could lower intracellular tyrosine levels to the point where TH was no longer fully saturated.…”

Serial changes in expression of functionally clustered genes in progression of liver fibrosis in hepatitis C patients

“…The first type of metabolism relates to the redox state [59] and the second is associated with production of active metabolites such as catecholamines and serotonin. Such important biological states are controlled to maintain homeostasis through several mechanisms [60] and this may explain the delayed change in expression of these genes. The expression of many genes related to intracellular signaling, including insulin/Wnt signaling, also changed simultaneously in the transition from F2 to F3.…”

Mutations in human monoamine-related neurotransmitter pathway genes

“…The phenylalanine hydroxylase (PAH), TH, and TPHs constitute a small family of closely related tetrahydrobiopterin cofactor-dependent aromatic amino acid hydroxylases [Fitzpatrick, 2000]. Although the conversion of PAH to tyrosine in dog liver was demonstrated in 1913 [Embden and Baldes, 1913], the first mammalian PAH was characterized around 1960.…”