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MS
PW-043 Amino Acid & Nitrogen Metabolism Anabolic + antioxidant unreviewed

Glutathione Metabolism (gamma-Glutamyl Cycle)

Glutamate + cysteine + glycine Glutathione (GSH); GSSG; mercapturic acids
Compartment
Cytosol
Main tissue
All cells; highest in liver and RBC
Rate-limiting
gamma-Glutamylcysteine synthetase (GCL)
Steps
5

Reaction steps

In source order, 5 total

showing 1–5
  1. 1

    L-Glutamate + L-cysteine + ATP -> gamma-glutamylcysteine + ADP + Pi

    › Notes

    Rate-limiting step; feedback-inhibited by GSH. Cysteine availability is usually the limiting substrate.

  2. 2

    gamma-Glutamylcysteine + glycine + ATP -> glutathione (GSH) + ADP + Pi

    Glutathione synthetase (GSS) 6.3.2.3 ST-0337 Irreversible/directional ATP
    › Notes

    Deficiency causes 5-oxoprolinuria (pyroglutamic aciduria) with haemolytic anaemia.

  3. 3

    2 GSH + H2O2 -> GSSG + 2 H2O

    Glutathione peroxidase (GPX) 1.11.1.9 ST-0338 Irreversible/directional Selenium
    › Notes

    Selenocysteine enzyme; the principal peroxide defence of the erythrocyte.

  4. 4

    GSSG + NADPH + H+ -> 2 GSH + NADP+

    Glutathione reductase (GSR) 1.8.1.7 ST-0339 Irreversible/directional NADPH FAD
    › Notes

    Links antioxidant defence to the pentose phosphate pathway; this is why G6PD deficiency causes oxidative haemolysis. Riboflavin (FAD) dependent.

  5. 5

    Xenobiotic/electrophile + GSH -> GS-conjugate -> mercapturic acid

    Glutathione S-transferase (GST) 2.5.1.18 ST-0340 Irreversible/directional GSH
    › Notes

    Phase II conjugation; depletion of GSH by NAPQI underlies paracetamol (acetaminophen) hepatotoxicity, treated with N-acetylcysteine.

Showing all 5 steps.

Recent literature

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    Lin Y, Yuan K, Liu Y, Du Y, Chang H, Hou L, Liang Y, Huang K, Yang S, Tang T. · 2026-08-18

    open access unreviewed
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    Ferroptosis in major depressive disorder: Molecular mechanisms, cellular vulnerability, and therapeutic opportunities.

    Kong D, Duan R, Wang X, Wang X, Zhao J. · 2026-09-18

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    Responses of arbuscular mycorrhizal wheat to salinity: from symbiotic signaling to stress adaptation.

    Zamir H, Rauf F, Jamali ZH, Khan S, Zulfiqar U, Alotaibi MS, Muminov M, Abdusamatov S, Gururani MA, Korai SK. · 2026-09-23

    open access unreviewed
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    Metabolic regulation of oocyte maturation and early embryo development in mammals.

    Rong S, Fu Y, Li Y, Jiang YC, Chen L, Zhao Y, Zhu W, Mu L. · 2026-08-06

    open access unreviewed
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    From molecules to medicine: the gut‒heart axis comes of age.

    Pretorius T, Marques FZ. · 2026-09-19

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External claims. These come from an index outside this database and are not checked against it. Treat them as leads.