Abstract
Peroxiredoxin is an abundant peroxidase, but its non-peroxidase function is also important. In this study, we discovered that Tsa1, a major peroxiredoxin of budding yeast cells, is required for the efficient flux of gluconeogenesis. We found that the suppression of pyruvate kinase (Pyk1) via the interaction with Tsa1 contributes in part to gluconeogenic enhancement. The physical interactions between Pyk1 and Tsa1 were augmented during the shift from glycolysis to gluconeogenesis. Intriguingly, a peroxidatic cysteine in the catalytic center of Tsa1 played an important role in the physical Tsa1-Pyk1 interactions. These interactions are enhanced by exogenous H2O2 and by endogenous reactive oxygen species, which is increased during gluconeogenesis. Only the peroxidatic cysteine, but no other catalytic cysteine of Tsa1, is required for efficient growth during the metabolic shift to obtain maximum yeast growth (biomass). This Tsa1 function is separable from the peroxidase function as an antioxidant. This is the first report to demonstrate that peroxiredoxin has a novel nonperoxidase function as a redox-dependent target modulator and that pyruvate kinase is modulated via an alternative mechanism.
Highlights
Peroxiredoxin (Prx) is a member of a family of thioredoxin-dependent peroxidases found in species ranging from Escherichia coli to humans[1,2]
We demonstrate that the peroxidatic cysteine of Tsa[1], which participates in its interaction with Pyk[1], has a crucial role in achieving an efficient shift from glycolysis to gluconeogenesis
The improved understanding of the Tsa1-dependent regulatory mechanism of Pyk[1] provides evidence for an alternative role of the peroxidatic cysteine Cys[48] of Tsa[1] in efficient gluconeogenesis. This finding is further supported by the ability of Tsa1C171T expression to almost completely recover the growth retardation and to almost restore the levels of trehalose/glycogen during the diauxic shift in glucose medium (Fig. 8)
Summary
Peroxiredoxin (Prx) is a member of a family of thioredoxin-dependent peroxidases found in species ranging from Escherichia coli to humans[1,2]. We reported that lowering ROS levels does not functionally compensate for the loss of Tsa[1], leading us to speculate that its role in carbon metabolism is likely due to a non-peroxidase function of Tsa[15]. Pyruvate kinase (PK) catalyzes an irreversible reaction that generates ATP and pyruvate from phosphoenolpyruvate (PEP) and ADP as the final step in glycolysis (see Fig. 1A for the metabolic map), and it is essential when a fermentable carbon source such as glucose is used[10]. Pyk[1] plays an important role in the synthesis of several amino acids from pyruvate via gluconeogenesis using ethanol as a carbon source[14]. Our results suggest a novel regulatory mechanism for Pyk[1] and an alternative non-antioxidant function of Tsa[1] (Prx)
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