Figure 7.
Scheme of the de novo synthesis pathway of glutathione. (A) based on 13C6 glucose and (B) on 13C515N glutamic acid as tracers. Red circles, 13C6; black circles, 12C6. CBS, cystathionine b-synthetase; CTH, cystathionase; GCL, glutamate-cysteine ligase; GSS, glutathione synthetase; GPx, glutathione peroxidase; GR, glutathione reductase; GSSG, oxidized GSH. Of note, GSSG can exist in three versions in parallel, as it is made of two GSH molecules: 13C6, 13C3, and 12C when 13C6 glucose is the tracer and 13C1015N2, 13C515N, and 12C14N when 13C515N glutamic acid is the tracer.