Role of Yeast Glutaredoxins as Glutathione S-transferases

Abstract

The yeast Saccharomyces cerevisiae contains two glutaredoxins, encoded by GRX1 and GRX2, that are required for resistance to reactive oxygen species. We recently reported that Grx1 is active as a glutathione peroxidase and can directly reduce hydroperoxides (Collinson, E. J., Wheeler, G. L., Garrido, E. O., Avery, A. M., Avery, S. V., and Grant, C. M. (2002) J. Biol. Chem. 277, 16712-16717). We now show that Grx2 is also a general hydroperoxidase, and kinetic data indicate that both enzymes have a similar pattern of activity, which is highest with hydrogen peroxide, followed by cumene hydroperoxide and tert-butyl hydroperoxide. Furthermore, both Grx1 and Grx2 are shown be active as glutathione S-transferases (GSTs), and their activity with model substrates such as 1-chloro-2,4-dinitrobenzene is similar to their activity with hydroperoxides. Analysis of the Grx1 active site residues shows that Cys-27, but not Cys-30, is required for both the peroxidase and transferase activities, indicating that these reactions proceed via a monothiol mechanism. Deletion analysis shows that Grx1 and Grx2 have an overlapping function with yeast GSTs, encoded by GTT1 and GTT2, and are responsible for the majority of cellular GST activity. In addition, multiple mutants lacking GRX1, GRX2, GTT1, and GTT2 show increased sensitivity to stress conditions, including exposure to xenobiotics, heat, and oxidants. In summary, glutaredoxins are multifunctional enzymes with oxidoreductase, peroxidase, and GST activity, and are therefore ideally suited to detoxify the wide range of xenobiotics and oxidants that can be generated during diverse stress conditions.

The Dithiol Glutaredoxins of African Trypanosomes Have Distinct Roles and Are Closely Linked to the Unique Trypanothione Metabolism

“…Grx1 and Grx2 Lack Peroxidase Activity-Saccharomyces cerevisiae Grx1 has been reported to be an efficient general glutathione peroxidase (37). In trypanosomes, hydroperoxide reduction is catalyzed by a cascade composed of NADPH, TR, T(SH) 2 , Tpx, and either TXNPx or Px III, which both act as tryparedoxin peroxidases (17).…”

“…Alternatively, the assays contained 10 M Tpx plus 10 M Grx1 or Grx2. In analogy to the peroxidase assays described for yeast Grxs (37), the third type of assays lacked Tpx and Px III but contained 50 M Grx1 or Grx2.…”

Insights into Deglutathionylation Reactions

“…Multiple glutaredoxins are known in different organisms (8 -12), but the role of these proteins in cells and in different cell organelles is still unclear. Glutaredoxins are thought to have a primary role in defense against oxidative stress (13)(14)(15)(16)), but they have been suggested to participate in other functions, such as cellular differentiation (17), redox regulation of signal transduction (14,18) and prevention of apoptosis (15).…”

Targeting Genes of Cd Induced Oxidative Stress Response in Yeasts

“…Moreover, one general mechanism for cadmium detoxification, both in S. cerevisiae and mammals, is the chelation of the metal by glutathione and the subsequent compartmentalization of the GSh-metal complex (33). Many xenobiotics can react either spontaneously with the thiol moiety of GSh to form GSh-conjugates, or via glutathione S-transferases (9,18). Analysis of the genome of the studied yeast strains revealed that C. glabrata, P. pastoris and H. polymorpha have only one glutathione S-transferase orthologous either to GTT1, or to GTT3 (Table 2 and Fig.…”

“…in this respect R. graminis and especially S. pombe possess obvious advantages in comparison to other yeast strains. however, research carried out by collinson and Grant (9) showed that in S. cerevisiae two other proteins, namely Grx1p and Grx2p, have an overlapping function with that of glutathione S-transferases and are primarily responsible for intracellular glutathione S-transferase activity. thus, cells that lack glutathione S-transferases can probably also carry out the disposal of various xenobiotics and heavy metals by alternative expression of multifunctional glutaredoxins.…”