Amino Acids

, Volume 7, Issue 3, pp 279–289 | Cite as

Destabilization of tyrosine aminotransferase by amino acids

  • J. L. Hargrove
  • C. Liu


Several L-amino acids (tyrosine, glutamate, methionine, tryptophan, and phenylalanine) and penicillamine destabilized purified tyrosine aminotransferase by removing enzyme-bound pyridoxal 5′-phosphate. The destabilization was measured as a progressive loss of enzyme activity in samples taken at intervals from a primary mixture that was incubated at 37°C. Each destabilizing amino acid either served as a substrate for this enzyme or was a product of transamination. In contrast, L-cysteine destabilized the enzyme only if liver homogenate was added, which generated polysulfide by desulfuration. Cysteine complexed free pyridoxal-5′-phosphate but did not remove it from the enzyme. Other amino acids did not destabilize tyrosine aminotransferase at the concentrations tested.


Amino acids Glutamate Cysteine Apoenzyme Tyrosine aminotransferase 



tyrosine aminotransferase (E.C.




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Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • J. L. Hargrove
    • 1
  • C. Liu
    • 1
  1. 1.Department of Foods and NutritionUniversity of GeorgiaAthensUSA

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