Quantitative analysis of sulfur-related metabolites during cadmium stress response in yeast by capillary electrophoresis–mass spectrometry

The objective of this research is to establish an evaluation system of metabolites by capillary electrophoresis–mass spectrometry (CE–MS) in response to chemical stress using the unicellular genome model, yeast (Saccharomyces cerevisiae strain S288C). A method previously reported by Soga et al. was modified and validated for the determination of sulfur-related metabolites, 23 cationic metabolites, in yeast extract. A mixture of 5 mM formic acid in 50% (v/v) 2-propanol was used for the sheath liquid to improve the detection sensitivity. Moreover, washing of CE capillary with 0.1 M ammonia solution between successive runs enhanced the reproducibility. After analytical validation, the method was applied to the metabolomic analysis of yeast cells in response to cadmium (Cd) stress. Under Cd exposure, some interesting observations were obtained, particularly the depletion of glycine and the strong accumulation of l-γ-glutamylcysteine in yeast cells.