Correction: Effect of curcuminoids and curcumin derivate products on thioredoxin-glutathione reductase from Taenia crassiceps cysticerci. Evidence suggesting a curcumin oxidation product as a suitable inhibitor

Mitochondrial thioredoxin-glutathione reductase was purified from larvalTaenia crassiceps(cysticerci). The preparation showed NADPH-dependent reductase activity with either thioredoxin or GSSG, and was able to perform thiol/disulfide exchange reactions. At25∘Cspecific activities were437 ± 27mU mg-1and840 ± 49mU mg-1with thioredoxin and GSSG, respectively. ApparentKmvalues were0.87 ± 0.04 μM,41 ± 6 μM and19 ± 10 μM for thioredoxin, GSSG and NADPH, respectively. Thioredoxin from eukaryotic sources was accepted as substrate. The enzyme reduced H2O2in a NADPH-dependent manner, although with low catalytic efficiency. In the presence of thioredoxin, mitochondrial TGR showed a thioredoxin peroxidase-like activity. All disulfide reductase activities were inhibited by auranofin, suggesting mTGR is dependent on selenocysteine. The reductase activity with GSSG showed a higher dependence on temperature as compared with the DTNB reductase activity. The variation of the GSSG- and DTNB reductase activities on pH was dependent on the disulfide substrate. Like the cytosolic isoform, mTGR showed a hysteretic kinetic behavior at moderate or high GSSG concentrations, but it was less sensitive to calcium. The enzyme was able to protect glutamine synthetase from oxidative inactivation, suggesting that mTGR is competent to contend with oxidative stress.

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Reaction Mechanism and Regulation of Mammalian Thioredoxin/Glutathione Reductase†

Biochemistry ◽

10.1021/bi051321w ◽

2005 ◽

Vol 44 (44) ◽

pp. 14528-14537 ◽

Cited By ~ 54

Author(s):

Qi-An Sun ◽

Dan Su ◽

Sergey V. Novoselov ◽

Bradley A. Carlson ◽

Dolph L. Hatfield ◽

...

Keyword(s):

Reaction Mechanism ◽

Glutathione Reductase ◽

Thioredoxin Glutathione Reductase

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Insight into the Mechanistic Basis of the Hysteretic-Like Kinetic Behavior of Thioredoxin-Glutathione Reductase (TGR)

Enzyme Research ◽

10.1155/2018/3215462 ◽

2018 ◽

Vol 2018 ◽

pp. 1-17 ◽

Cited By ~ 1

Author(s):

Juan L. Rendón ◽

Mauricio Miranda-Leyva ◽

Alberto Guevara-Flores ◽

José de Jesús Martínez-González ◽

Irene Patricia del Arenal ◽

...

Keyword(s):

Glutathione Reductase ◽

Reductase Activity ◽

Active Form ◽

Kinetic Mechanism ◽

Product Inhibition ◽

Hysteretic Behavior ◽

Low Concentrations ◽

Mechanistic Basis ◽

High Concentrations ◽

Thioredoxin Glutathione Reductase

A kinetic study of thioredoxin-glutathione reductase (TGR) from Taenia crassiceps metacestode (cysticerci) was carried out. The results obtained from both initial velocity and product inhibition experiments suggest the enzyme follows a two-site ping-pong bi bi kinetic mechanism, in which both substrates and products are bound in rapid equilibrium fashion. The substrate GSSG exerts inhibition at moderate or high concentrations, which is concomitant with the observation of hysteretic-like progress curves. The effect of NADPH on the apparent hysteretic behavior of TGR was also studied. At low concentrations of NADPH in the presence of moderate concentrations of GSSG, atypical time progress curves were observed, consisting of an initial burst-like stage, followed by a lag whose amplitude and duration depended on the concentration of both NADPH and GSSG. Based on all the kinetic and structural evidence available on TGR, a mechanism-based model was developed. The model assumes a noncompetitive mode of inhibition by GSSG in which the disulfide behaves as an affinity label-like reagent through its binding and reduction at an alternative site, leading the enzyme into an inactive state. The critical points of the model are the persistence of residual GSSG reductase activity in the inhibited GSSG-enzyme complexes and the regeneration of the active form of the enzyme by GSH. Hence, the hysteretic-like progress curves of GSSG reduction by TGR are the result of a continuous competition between GSH and GSSG for driving the enzyme into active or inactive states, respectively. By using an arbitrary but consistent set of rate constants, the experimental full progress curves were successfully reproduced in silico.

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