Phenylketonuric Tetrahymena: phenylalanine hydroxylase mutants and other tyrosine auxotrophs.

Phenylketonuric Tetrahymena: phenylalanine hydroxylase mutants and other tyrosine auxotrophs.

Nineteen tyrosine auxotrophs of the ciliated protozoan Tetrahymena thermophila have been isolated and biochemically examined. These mutants are defective in the conversion of phenylalanine to tyrosine; this is analogous to the defect that causes phenylketonuria in humans. After nitrosoguanidine mutagenesis and self-fertilization, progeny clones were screened for tyrosine auxotrophy and positive...

Phenylalanine Hydroxylase, Tyrosine Hydroxylase, and Tryptophan Hydroxylase

Enzyme alterations in tyrosine and phenylalanine auxotrophs of Salmonella typhimurium.

The enzyme activities specified by the tyrA and pheA genes were studied in wildtype strain Salmonella typhimurium and in phenylalanine and tyrosine auxotrophs. As in Aerobacter aerogenes and Escherichia coli, the wild-type enzymes of Salmonella catalyze two consecutive reactions: chorismate --> prephenate --> 4-hydroxy-phenylpyruvate (tyrA), and chorismate --> prephenate --> phenylpyruvate (phe...

Mouse phenylalanine hydroxylase. Homology and divergence from human phenylalanine hydroxylase.

The laboratory mouse represents an important model for the study of phenylalanine metabolism and the pathochemistry of phenylketonuria, yet mouse phenylalanine hydroxylase (PAH) has not been extensively studied. We report the cloning and sequencing of a mouse PAH cDNA, the expression of enzymic activity from the mouse PAH cDNA clone and the identification of mouse PAH and human PAH by two-dimen...

Liver phenylalanine hydroxylase activity in relation to blood concentrations of tyrosine and phenylalanine in the rat.

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...