Synthesis and activity of the glutathione analogue γ‐(L‐γ‐azaglutamyl)‐L‐cysteinyl‐glycine

Abstract
The backbone-modified glutathione analogue γ-(L-γ-azaglutamyl)-L-cysteinyl-glycine 7, characterized by the presence of a NHCONH urea linkage deriving from the replacement of the native Glu γ-CH2 with the aza (NH) group, was synthesized and fully characterized by FAB-MS, 1H- and 13C-NMR. Potential of 7 and its oxidized form 6 as γ-glutamyltransferase inhibitors was investigated. Both compounds 7 and 6 were found to be competitive inhibitors of hog kidney y-glutamyltransferase (EC 2.3.2.2.) by binding at the donor site: the reduced analogue is a more efficient inhibitor than glutathione of the γ-glutamyl transfer reaction. Inhibition at the acceptor site, which is also present, appears to be more complex. In particular, un-competitive inhibition is observed for compound 7. The results indicate that γ-azapeptides of type 7 may represent interesting targets in the search for stable inhibitors of γ-glutamyltransferases. © Munksgaard 1995.

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