Direct Monitoring of γ‐Glutamyl Transpeptidase Activity In Vivo Using a Hyperpolarized 13C‐Labeled Molecular Probe

Abstract The γ‐glutamyl transpeptidase (GGT) enzyme plays a central role in glutathione homeostasis. Direct detection of GGT activity could provide critical information for the diagnosis of several pathologies. We propose a new molecular probe, γ‐Glu‐[1‐ 13 C]Gly, for monitoring GGT activity in vivo by hyperpolarized (HP) 13 C magnetic resonance (MR). The properties of γ‐Glu‐[1‐ 13 C]Gly are suitable for in vivo HP 13 C metabolic analysis since the chemical shift between γ‐Glu‐[1‐ 13 C]Gly and its metabolic product, [1‐ 13 C]Gly, is large (4.3 ppm) and the T 1 of both compounds is relatively long (30 s and 45 s, respectively, in H 2 O at 9.4 T). We also demonstrate that γ‐Glu‐[1‐ 13 C]Gly is highly sensitive to in vivo modulation of GGT activity induced by the inhibitor acivicin.