Posttranslational Modification of Human Glyoxalase 1 Indicates Redox-Dependent Regulation

Abstract

BackgroundGlyoxalase 1 (Glo1) and glyoxalase 2 (Glo2) are ubiquitously expressed cytosolic enzymes that catalyze the conversion of toxic α-oxo-aldehydes into the corresponding α-hydroxy acids using L-glutathione (GSH) as a cofactor. Human Glo1 exists in various isoforms; however, the nature of its modifications and their distinct functional assignment is mostly unknown.Methodology/Principal FindingsWe characterized native Glo1 purified from human erythrocytes by mass spectrometry. The enzyme was found to undergo four so far unidentified posttranslational modifications: (i) removal of the N-terminal methionine 1, (ii) N-terminal acetylation at alanine 2, (iii) a vicinal disulfide bridge between cysteine residues 19 and 20, and (iv) a mixed disulfide with glutathione on cysteine 139. Glutathionylation of Glo1 was confirmed by immunological methods. Both, N-acetylation and the oxidation state of Cys19/20, did not impact enzyme activity. In contrast, glutathionylation strongly inhibited Glo1 activity in vitro. The discussed mechanism for enzyme inhibition by glutathionylation was validated by molecular dynamics simulation.Conclusion/SignificanceIt is shown for the first time that Glo1 activity directly can be regulated by an oxidative posttranslational modification that was found in the native enzyme, i.e., glutathionylation. Inhibition of Glo1 by chemical reaction with its co-factor and the role of its intramolecular disulfides are expected to be important factors within the context of redox-dependent regulation of glucose metabolism in cells.

daf-16/FOXO and glod-4/glyoxalase-1 are required for the life-prolonging effect of human insulin under high glucose conditions in Caenorhabditis elegans

“…Insulin-mediated increased glyoxalase-1 activity could be caused by the lowering of glucose and ROS, preserving glutathione as an essential cofactor. Alternatively, insulin might restore the enzyme activity by enhancing other antioxidant defence systems, thereby preventing the loss of function caused by post-translational modifications, since glyoxalase-1 activity can be reduced by post-translational modifications [37]. As glod-4 mRNA levels are not directly affected by treatment with human insulin we postulate an indirect mechanism.…”

Protein S-Glutathionylation in Malaria Parasites

“…S1). Interestingly, human cytosolic glyoxalase I is strongly inhibited by Sglutathionylation on cysteine 139 (corresponding to Cys311 in PfcGloI) (6). However, S-glutathionylation of PfLDH, PfcGloI, and PfcGloII might influence their oligomerization behavior or protein-protein interactions, which remains to be studied in detail.…”

Glyoxalase I in Tumor Cell Proliferation and Survival and as a Potential Target for Anticancer Therapy

“…Decreased activity and increased degradation of GLO1 mediated by antitumor agents were shown to give rise to impaired methylglyoxal metabolism [35,36]. An increased rate of methylglyoxal formation and a decreased rate of methylglyoxal metabolism lead to an elevated level of intracellular methylglyoxal.…”