Lysine241 of tyrosine hydroxylase is not required for binding of tetrahydrobiopterin substrate

S. Colette Daubner, Paul F. Fitzpatrick

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Abstract

The lysine residues at positions 194 and 198 in phenylalanine hydroxylase have been shown to react with a photoaffinity label which is an analog of phenyltetrahydropterin (Gibbs, B. S., and Benkovic, S. J. (1991) Biochemistry 30, 6795-6802), in a manner suggesting that these lysine residues are involved in tetrahydrobiopterin binding. The related enzyme tyrosine hydroxylase has a lysine at position 241 which, given the 75% identity between its C-terminal 330 amino acids and those of phenylalanine hydroxylase, corresponds to lysinel94 of phenylalanine hydroxylase. Site-directed mutagenesis was used to alter lysine241 of tyrosine bydroxylase to alanine. Steady-state kinetic parameters were measured for wild-type and K241A tyrosine bydroxylase. No kinetic parameter differed between the wild-type and K241A enzymes, including Vmax values, Michaelis constants for tetrahydrobiopterin, 6-methyl-tetrahydropterin, and tyrosine, and the inhibition constants for norepinephrine. These results show that lysine241 is not required for tetrahydrobiopterin binding to tyrosine hydroxylase.

Original languageEnglish (US)
Pages (from-to)455-460
Number of pages6
JournalArchives of Biochemistry and Biophysics
Volume302
Issue number2
DOIs
Publication statusPublished - Jan 1 1993

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ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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