Zinc is required for many critical processes, including intermediary metabolism. In Saccharomyces cerevisiae, the Zap1 activator regulates the transcription of approximately 80 genes in response to Zn supply. Some Zap1-regulated genes are Zn transporters that maintain Zn homeostasis, while others mediate adaptive responses that enhance fitness. One adaptive response gene encodes the 2-cysteine peroxiredoxin Tsa1, which is critical to Zn-deficient (ZnD) growth. Depending on its redox state, Tsa1 can function as a peroxidase, a protein chaperone, or a regulatory redox sensor. In a screen for possible regulatory Tsa1 targets, we identified a mutation (cdc19(S492A)) that partially suppressed the tsa1Delta growth defect. The cdc19(S492A) mutation reduced activity of its protein product, pyruvate kinase isozyme 1 (Pyk1), implicating Tsa1 in adapting glycolysis to ZnD conditions. Glycolysis requires activity of the Zn-dependent enzyme fructose-bisphosphate aldolase (Fba1), which was substantially decreased in ZnD cells. We hypothesized that in ZnD tsa1Delta cells, the loss of a compensatory Tsa1 regulatory function causes depletion of glycolytic intermediates and restricts dependent amino acid synthesis pathways, and that the decreased activity of Pyk1(S492A) counteracted this depletion by slowing the irreversible conversion of phosphoenolpyruvate to pyruvate. In support of this model, supplementing ZnD tsa1Delta cells with aromatic amino acids improved their growth. Phosphoenolpyruvate supplementation, in contrast, had a much greater effect on growth rate of wild-type and tsa1Delta ZnD cells, indicating that inefficient glycolysis is a major factor limiting yeast growth. Surprisingly however, this restriction was not primarily due to low Fba1 activity, but instead occurs earlier in glycolysis.

• PMID: 38460940
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Journal Article

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MacDiarmid CW, Taggart J, Kubisiak M, Eide DJ

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