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Isolation and characterization of active N‐terminal truncated apo‐ and holoenzyme of mammalian liver tyrosine aminotransferase
Author(s) -
Lorber Bernard,
Dietrich Jean-Bernard,
Kern Daniel
Publication year - 1991
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 - 10.1016/0014-5793(91)81317-2
Subject(s) - tyrosine aminotransferase , tyrosine , thermostability , biochemistry , proteolysis , enzyme , pyridoxal , trypsin , chemistry , biology , enzyme inducer
Limited proteolysis was used to probe the structure of the apo‐ and holoenzyme of rat liver tyrosine aminotransferase. Both were subjected to trypsinolysis and the major fragments were isolated and characterized. Trypsin cleaves the apoenzyme after residues Arg 57 , Lys 64 , and Lys 71 and the holoenzyme after Arg 37 and Lys 38 . The difference in the accessibility of the enzyme deprived or associated with pyridoxal 5′‐phosphate reflects two distinct conformations. The activity, the affinity for the ligands and the thermostability of the purified truncated enzyme forms are similar to those of the native apo‐ and holoenzyme. A model for the domain structure of mammalian tyrosine aminotransferase and a mechanism for its rapid turnover are proposed.