Recent studies have shown that a subgroup of phenylketonuric patients respond to high doses of BH4 (20 mg/kg) by a decrease of plasma phenylalanine. A clinically significant response has been defined as a decrease in phenylalanine by more than 30% within 24 h, after a BH4 challenge. We report our experience with 37 patients diagnosed with hyperphenylalaninemia, mild, moderate, or classical Phen...

Blood levels of the amino acid phenylalanine, as well as of the tryptophan breakdown product kynurenine, are found to be elevated in human immunodeficiency virus type 1 (HIV-1)-infected patients. Both essential amino acids, tryptophan and phenylalanine, are important precursor molecules for neurotransmitter biosynthesis. Thus, dysregulated amino acid metabolism may be related to disease-associa...

The interaction of L-phenylalanine with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air-water interface was explored using a combination of experimental techniques and molecular dynamics (MD) simulations. By means of Langmuir trough methods and Brewster angle microscopy, L-phenylalanine was shown to significantly alter the interfacial tension and the surface domain mor...

A spectrophotometric recycling assay for the quantitation of L-phenylalanine (and phenylpyruvate) has previously been reported (Cooper et al., Anal. Biochem. 183, 210-214, 1989). The procedure involves the coupling of bacterial phenylalanine dehydrogenase with rat kidney cytosolic glutamine transaminase K. The latter enzyme possesses high affinity for phenylpyruvate. Recycling results in a > or...

A monoclonal antibody (PH 7), which recognizes the phosphorylated form of phenylalanine hydroxylase from human liver, has been used for the analysis of the enzyme in crude cell extracts from rat. In immunoblot analyses of rat liver cell extracts, the extent of binding of PH 7 closely correlates with the phosphorylation state of phenylalanine hydroxylase, as judged by [32P]Pi incorporation. Thes...

Rat hepatic phenylalanine hydroxylase requires both a tetrahydropterin cofactor and molecular oxygen to convert phenylalanine to tyrosine. During the physiological hydroxylation, a single mol of the natural cofactor, tetrahydrobiopterin, is oxidized for each mol of phenylalanine converted to tyrosine. Artificial conditions have been devised in which the oxidation of the tetrahydropterin is unco...

Dual biosynthetic pathways to L-phenylalanine and Ltyrosine exist in Pseudomonas aeruginosa (Patel, N., Pierson, D. L., and Jensen, R. A. (197’7) J. Biol. Chem. 252, 5839-5846). Tightly blocked phenylalanine or tyrosine auxotrophs are not obtained as the result of single mutations. Presumably the presence of a mutation that interrupts one pathway is masked by the presence of the alternative pat...

1. Cell-free extracts of Escherichia coli K12 catalyse the synthesis of N-acetyl-l-phenylalanine from acetyl-CoA and l-phenylalanine. 2. The acetyl-CoA-l-phenylalanine alpha-N-acetyltransferase was purified 160-fold from cell-free extracts. 3. The enzyme has a pH optimum of 8 and catalyses the acetylation of l-phenylalanine. Other l-amino acids such as histidine and alanine are acetylated at sl...

Estimation of plasma phenylalanine and tyrosine by an abridged (30 mm) column chromatography procedure was assessed. Plasma phenylalanine and tyrosine concentrations, determined in 112 phenylketonuric obligate heterozygotes and in 88 normal controls, did not differ significantly from other reported series in which the data were obtained by column chromatography. All these series were combined a...

Phenylketonuria (PKU), an inborn error in phenylalanine metabolism, requires lifelong nutrition management with a low-phenylalanine diet, which includes a phenylalanine-free amino acid-based medical formula to provide the majority of an individual's protein needs. Compliance with this diet is often difficult for older children, adolescents, and adults with PKU. The whey protein glycomacropeptid...