Site-directed mutagenesis of tyrosine-71 to phenylalanine in Citrobacter freundii tyrosine phenol-lyase: evidence for dual roles of tyrosine-71 as a general acid catalyst in the reaction mechanism and in cofactor binding.

@article{Chen1995SitedirectedMO,
  title={Site-directed mutagenesis of tyrosine-71 to phenylalanine in Citrobacter freundii tyrosine phenol-lyase: evidence for dual roles of tyrosine-71 as a general acid catalyst in the reaction mechanism and in cofactor binding.},
  author={Hongmin Chen and Tatyana V. Demidkina and Robert S Phillips},
  journal={Biochemistry},
  year={1995},
  volume={34 38},
  pages={
          12276-83
        }
}
Tyr71 is an invariant residue in all known sequences of tyrosine phenol-lyase (TPL). The substitution of Tyr71 in TPL by phenylalanine results in a mutant Y71F TPL with no detectable activity (greater than 3 x 10(5)-fold reduction) for beta-elimination of L-tyrosine. Y71F TPL can react with S-alkylcysteines, but these substrates exhibit kcat values reduced by 10(3)-10(4)-fold, while the kcat/Km values are reduced by 10(2)-10(3)-fold, compared to wild-type TPL. However, for substrates with good… CONTINUE READING
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