BACKGROUND Phenylalanine and tyrosine are precursor amino acids required for the synthesis of dopamine, the main neurotransmitter implicated in the neurobiology of schizophrenia. Inflammation, increasingly implicated in schizophrenia, can impair the function of the enzyme Phenylalanine hydroxylase (PAH; which catalyzes the conversion of phenylalanine to tyrosine) and thus lead to elevated pheny...

Phenylalanine hydroxylase was prepared from human foetal liver and purified 800-fold; it appeared to be essentially pure. The phenylalanine hydroxylase activity of the liver was confined to a single protein of mol.wt. approx. 108000, but omission of a preliminary filtration step resulted in partial conversion into a second enzymically active protein of mol.wt. approx. 250000. Human adult and fu...

Phenylalanine hydroxylation is necessary for the conversion of phenylalanine to tyrosine and disposal of excess phenylalanine. Studies of in vivo regulation of phenylalanine hydroxylation suffer from the lack of a method to determine intrahepatocyte enrichment of phenylalanine and tyrosine. apoB-100, a hepatic export protein, is synthesized from intrahepatocyte amino acids. We designed an in vi...

It has recently been demonstrated that variability in blood phenylalanine levels is inversely correlated with IQ and is a better predictor of IQ in early and continuously treated patients with phenylketonuria (PKU) than mean blood phenylalanine levels. This suggests that stability of blood phenylalanine should be a therapeutic goal in patients with PKU. The purpose of this study was to determin...

Biogenic amines play an important role in brain metabolism and functioning, participation synaptic transmission as neurotransmitters neuromodulators (dopamine, serotonin, histamine others). Catecholamines are formed from the essential amino acid phenylalanine by hydroxylating it to tyrosine with enzyme phenylalanine-4-hydroxylase, which is subsequently converted dioxyphenylalanine (DOPA) tyrosi...

McKean, C. M. (1971). Archives of Disease in Childhood, 46, 608. Effects of totally synthetic, low phenylalanine diet on adolescent phenylketonuric patients. The long-term responses of 5 adolescent phenylketonuric patients to chemically-defined, synthetic diets with normal and low phenylalanine content were determined. The synthetic preparations were found capable of sustaining good health and ...

We have investigated the p-chlorophenylalanine-dependent loss of phenylalanine hydroxylase activity in cultured hepatoma cells. The similarity of the effect of p-chlorophenylalanine on phenylalanine hydroxylase in the hepatoma cells and that reported from studies in uiuo indicates that the loss of phenylalanine hydroxylase activity is due to a direct interaction of the amino acid analog-ue with...

The plasma concentration of phenylalanine and tyrosine decreases in normal rats during the first few postnatal days; subsequently, the concentration of phenylalanine remains more or less constant, whereas that of tyrosine exhibits a high peak on day 13. The basal concentrations of the two amino acids were not altered by injections of thyroxine or cortisol, except in 13-day-old rats, when an inj...

Two patients with phenylketonuria (PKU) requiring treatment were fed on low protein milks. Both had blood phenylalanine levels below 1200 micronmol/l (20mg/100 ml) until given a phenylalanine challenge. Phenylalanine content of mature breast milk may provide intakes similar to those used in treating PKU. Diagnosis of PKU is unlikely to be missed if screening is carried out on the sixth or seven...