Formation of N(ε)-(γ-glutamyl)-lysine isodipeptide in Chinese-hamster ovary cells

L. Fesus, E. Tarcsa

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18 Citations (Scopus)


N(ε)-(γ-Glutamyl)-lysine isodipeptide was detected in a protein-free fraction of Chinese-hamster ovary cells and their culture fluid by using radioactive lysine as a tracer. The identity of the isodipeptide was established by its separation on ion-exchange chromatography, analysis by h.p.l.c. after derivatization, recovery of lysine after acidic hydrolysis or after cleavage by a specific enzyme, namely γ-glutamylamine cyclotransferase. The amount of isodipeptide was raised (460 pmol/107 cells and 61 pmol/ml of culture fluid were observed as highest values) as the cell density increased. Effects of inhibitors of intracellular protein degradation have shown that the isodipeptide derives from cross-linking N(ε)-(γ-glutamyl)-lysine bonds formed by tissue transglutaminase. Estimated half-life values of cross-linked proteins were about 3 h. γ-Glutamylamine cyclotransferase, which may split the isodipeptide formed during the continuous turnover of cross-linked proteins, was also found in Chinese-hamster ovary cells. Isodipeptide may have been accumulated when either its generated amount is beyond the capacity of γ-glutamylamine cyclotransferase or it is generated in cell compartments where this enzyme is not present.

Original languageEnglish
Pages (from-to)843-848
Number of pages6
JournalBiochemical Journal
Issue number3
Publication statusPublished - 1989

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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