Reanalysis of the Involvement of Gamma-glutamyl Transpeptidase in the Cell Activation Process

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