Enzymatic Mechanisms in Gamma-Glutamyl Metabolism

Gamma-glutamyl metabolism centres on the transfer and hydrolysis of the γ-glutamyl bond, a key linkage in glutathione and related peptides. The principal catalysts of this pathway are γ-glutamyl transferases (GGTs), a family of N-terminal nucleophile hydrolases that undergo autocatalytic cleavage to form mature heterodimeric enzymes. Through a ping-pong mechanism, GGTs first form a γ-glutamyl enzyme intermediate and then resolve it by transferring the residue either to water (hydrolysis) or to an acceptor amino acid or peptide (transpeptidation). This dual activity underlies glutathione turnover, cysteine recycling and the uptake of γ-glutamyl compounds across membranes. Structural studies of mammalian and bacterial GGTs have revealed conformational dynamics within the active-site lid loop and the importance of key residues that stabilise transition states. Beyond homeostatic functions, γ-glutamyl metabolism is exploited in pharmaceutical and biotechnological contexts, including the enzymatic synthesis of bioactive compounds and the development of targeted inhibitors to modulate redox balance in disease. Recent advances in enzyme engineering, immobilisation techniques and mechanistic characterisation continue to expand both fundamental understanding and practical applications of this versatile enzyme family.

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Enzymatic Mechanisms in Gamma-Glutamyl Metabolism publication trend

The graph below shows the total number of articles in enzymatic mechanisms in gamma-glutamyl metabolism across all publications each year (not limited to Nature Index journals).

Technical terms

Gamma-glutamyl transferase (GGT): An enzyme that cleaves and transfers the γ-glutamyl moiety of glutathione to acceptor molecules or water.

Pseudo-ping-pong mechanism: A two-step catalytic cycle involving formation of an acyl-enzyme intermediate followed by nucleophilic attack to release products.

Autocatalytic processing: Post-translational self-cleavage of a precursor polypeptide to generate the active enzyme’s subunits.

Transpeptidation: Enzymatic transfer of a γ-glutamyl group from donor to acceptor amino acids or peptides.

Active-site lid loop: A flexible protein segment that undergoes conformational changes during substrate binding and catalysis.

N-terminal nucleophile hydrolase: A class of enzymes in which the N-terminal residue acts as the catalytic nucleophile in bond cleavage.

References

1. l‐Theanine Goes Greener: A Highly Efficient Bioprocess Catalyzed by the Immobilized γ‐Glutamyl Transferase from Bacillus subtilis. ChemSusChem (2023).
2. Characterizing and Tailoring the Substrate Profile of a γ‑Glutamyltransferase Variant. ACS Synthetic Biology (2024).
3. Bacterial Gamma-Glutamyl Transpeptidase, an Emerging Biocatalyst: Insights Into Structure–Function Relationship and Its Biotechnological Applications. Frontiers in Microbiology (2021).
4. Human γ-Glutamyl Transpeptidase 1 STRUCTURES OF THE FREE ENZYME, INHIBITOR-BOUND TETRAHEDRAL TRANSITION STATES, AND GLUTAMATE-BOUND ENZYME REVEAL NOVEL MOVEMENT WITHIN THE ACTIVE SITE DURING CATALYSIS*. Journal of Biological Chemistry (2015).
5. Autocatalytic Processing of γ-Glutamyltranspeptidase*. Journal of Biological Chemistry (2002).