First isolation of γ-L-glutamyl-γ-aminobutyric acid from bovine brains

Increased Intra‐ and Extracellular Concentrations of γ‐Glutamylglutamate and Related Dipeptides in the Ischemic Rat Striatum: Involvement of γ‐Glutamyl Transpeptidase

“…Among other related reactions, y-GT catalyzes a transpeptidation reaction in which the y-glutamyl moiety of glutathione (GSH) is transferred to an extracellular acceptor amino acid (Hanes et al, 1952) according to: L-amino acid + GSH y-glutamyl-L-amino acid + cysteinylglycine This ATP-independent reaction, which takes place on the external surface of the membrane, results in transport of the y-glutamyl dipeptide into the cell (Meister and Tate, 1976;. Although this dipeptide synthesis/amino acid uptake route has not unequivocally been demonstrated in the mammalian CNS, the presence of numerous y-glutamyl dipeptides in brain (Sano et al, 1966;Reichelt, 1970;Sano, 1970;Mamela et al, 1985;Yamamoto et al, 1992;Sandberg et al, 1994) indicates that y-GT may be active in amino acid uptake . Inhibition of y-GT has, however, given contradictory results, i.e., both decreased Glu uptake (Lisy et al, 1983 ;Jankaskova et al, 1992) and unchanged uptake of Glu and Gln (Johansen et al, 1987), have been reported .…”