Reanalysis of the involvement of γ-glutamyl transpeptidase in the cell activation process

The inhibitor of γ-glutamyl transpeptidase (γ-GT) acivicin modulates cellular responses including growth, myeloid maturation and apoptosis. Whether these effects result from the inhibition of γ-GT enzyme activity remains unclear. We compared the cellular effects of acivicin against a more potent and specific inhibitor of γ-GT (L-2-amino-4-boronobutanoic acid (L-ABBA)) in γ-GT-negative (B lymphoblastoid Ramos) and γ-GT-positive (myelomonocytic HL-60, γ-GT-transfected Ramos) cell lines. Under non-oxidative stress conditions, acivicin-induced cell growth arrest, apoptosis and macrophage maturation occurred independent of γ-GT while L-ABBA did not influence any of these processes. Acivicin triggered tyrosine phosphorylation and increased nuclear factor κB activity. Further insight into the role of γ-GT in cellular processes is needed.