Effects on GSH synthesis in Chinese cabbage when the culturing solution is supplemented with ammonium sulfate or the constituent amino acids for glutathione

We examined the effects of the constituent amino acids for glutathione (GSH) - glutamate (Glu), cysteine (Cys), and glycine (Gly) - on GSH synthesis in Chinese cabbage seedlings. Glu, Cys, and Gly were applied simultaneously (100 mg L^-1) to the culture solution for 2 d. When compared with the control, GSH concentrations were increased by 2.1-fold (640.4 nmol g ^-1 FW) and 1.5-fold (416.4 nmol g^-1 FW) in the first leaf and the roots, respectively. Of all the free amino acids, the non-essentials, including Glu, Cys and Gly, occupied 95.5% (shoots) and 81.9% (roots) of the total. Cys supplements greatly enhanced the GSH concentration in the roots; application of 100 mg L^-1 increased the level by 7-fold over the control. The activity of GSH synthetase was higher in the roots than in the leaf, whereas that of γ-glutamylcysteine synthetase was higher in the leaf.