Fig. 3

The proposed molecular mechanisms by which functional amino acids improve the antioxidant capacity of swine. Arginine supplementation in swine can be catalyzed to ornithine, and then transfer into glutamate, which conjugates cysteine to generate γ-glutamyl cysteine that finally conjugates glycine to form GSH to improve the antioxidant capacity. Supplemented with glutamate, cysteine and glycine, or its precursors glutamine and NAC in swine can also improve the antioxidant capacity via GSH synthesis. Arginine, taurine and NAC can perform antioxidant effects through the activation of Nrf2 pathway, and arginine can also improve antioxidant capacity of swine via NO synthesis stimulated by NOS. NAC: N-acetylcysteine; ARG: arginase; NOS: oxide synthase; NO: nitric oxide; GS: synthase; GSH: glutathione; Nrf2: nuclear factor erythroid 2 (NF-E2)-related factor 2; Keap1: Kelch-like ECH-associated protein 1; Cul3: Cullin3; ARE: antioxidant responsive element; GPx: glutathione peroxidase; SOD: superoxide dismutase; CAT: catalase; GCLC: glutamate cysteine ligase catalytic; GCLM: glutamate cysteine ligase modifier; HO-1: heme oxygenase; NQO1: NAD(P)H:quinone oxidoreductase 1