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 vivo indicates that the loss of phenylalanine hydroxylase activity is due to a direct interaction of the amino acid analogue with ...

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism resulting from deficiency hydroxylase (PAH).

Rats were given intraperitoneal injections of 2 mCi of carrier-free "Pi and substances known to activate liver phenylalanine hydroxylase. After 30 min, these animals were anesthetized and their livers removed for analysis of enzyme activity, 32Pi ncorporation into immunoprecipitated phenylalanine hydroxylase and [yS2P]ATP specific activity. Following glucagon treatment, rat liver phenylalanine ...

The rate of release of deuterons into the body water from 2,3,4,5,6-pentadeutero-L-phenylalanine has been shown to be a valid measure of the activity of the phenylalanine hydroxylase system in vivo. At a dose of 0.5 g/kg, the rate of release of deuterons is linear for 60 to 90 min. Male rats, which had previously been shown to have 22 to 25% more phenylalanine hydroxylase activity in liver extr...

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...

Moderate doses of glucagon (20 micrograms/kg I.V.) are sufficient to stimulate rat hepatic phenylalanine hydroxylase in vivo. In addition, the stimulation of the tetrahydrobiopterin-dependent phenylalanine hydroxylase activity in livers of animals fed on a high-protein diet has been correlated with an elevated phosphate content. The tetrahydrobiopterin-dependent hydroxylase activity in these an...

background: phenylketonuria (pku) is an autosomal recessive disease of phenylalanine metabolism that brings deficiency of the enzyme phenylalanine hydroxylase (pah). early diagnosis is very important to prevent complications. this study was designed to describe characteristics of patients with phenylketonuria in mazandaran province in northern iran. methods: we studied 24 cases suffering from p...

Phenylalanine hydroxylase was shown to be inhibited by oudenone and its derivatives in vitro. At a concentration of 2.3 x 10(-3) M, oudenone inhibited phenylalanine hydroxylase by 50%, and some of the oudenone derivatives showed more potent inhibition. The kinetic data have shown that the inhibition by oudenone is competitive with a tetrahydropterin cofactor (6,7-dimethyltetrahydropterin, DMPH4...

The pH optimum of rat liver phenylalanine hydroxylase is dependent on the structure of the cofactor employed and on the state of activation of the enzyme. The tetrahydrobiopterin-dependent activity of native phenylalanine hydroxylase has a pH optimum of about 8.5. In contrast, the 6,7-dimethyltetrahydropterin-dependent activity is highest at pH 7.0. Activation of phenylalanine hydroxylase eithe...