title: Destabilization of tyrosine aminotransferase by amino acids.
abstract: 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.
authors.affiliation: Department of Foods and Nutrition, University of Georgia, 30602, Athens, GA, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Hargrove
authors.forename: C
authors.initials: C
authors.lastname: Liu