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Radiation target analysis indicates that phenylalanine hydroxylase in rat liver extracts is a functional monomer
Author(s) -
Parniak Michael A,
Davis Michael,
Kaufman Seymour,
Kempner Ellis S
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00392-0
Subject(s) - phenylalanine hydroxylase , tetrahydrobiopterin , tetramer , chemistry , enzyme , dimer , cofactor , phenylalanine , biochemistry , in vivo , monomer , in vitro , stereochemistry , biology , organic chemistry , amino acid , microbiology and biotechnology , polymer
The minimal enzymatically functional form of purified rat hepatic phenylalanine hydroxylase (PAH) is a dimer of identical subunits. Radiation target analysis of PAH revealed that the minimal enzymatically active form in crude extracts corresponds to the monomer. The ‘negative regulation' properties of the tetrahydrobiopterin cofactor in both crude and pure samples implicates a large multimeric structure, minimally a tetramer of PAH subunits. Preincubation of the samples with phenylalanine prior to irradiation abolished this inhibition component without affecting the minimal functional unit target sizes of the enzyme in both preparations. The characteristics of rat hepatic PAH determined by studies of the purified enzyme in vitro may not completely represent the properties of PAH in vivo.