Unravelling glutathione conjugate catabolism in Saccharomyces cerevisiae: the role of glutathione/dipeptide transporters and vacuolar function in the release of volatile sulfur compounds 3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one

• Published in: Applied microbiology and biotechnology Vol. 99; no. 22; pp. 9709 - 9722
• Main Authors: Cordente, Antonio G, Capone, Dimitra L, Curtin, Chris D
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2015; Springer; Springer Nature B.V
• Subjects: acetates; alcoholic fermentation; Amino acids; Analysis; Applied Genetics and Molecular Biotechnology; biogenesis; Biomedical and Life Sciences; Biotechnology; Biotransformation; Cadmium; cytosol; extracellular space; Fermentation; flavor; Flavors; Fruit juices; Genes; glutathione; Glutathione - metabolism; grape juice; GSH; Hostages; Laboratories; Life Sciences; Membrane Transport Proteins - metabolism; Microbial Genetics and Genomics; Microbiology; Monosaccharide Transport Proteins - metabolism; odor compounds; Pentanones - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - metabolism; Studies; Sulfhydryl Compounds - metabolism; Sulfur; Thiols; transporters; vacuoles; Vacuoles - metabolism; Vitaceae; Wine; Wines; Yeast; yeasts; Wine; conjugate; Yeast; Fermentation; Volatile thiols; Glutathione; Glutathione-S-conjugate
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-015-6833-5

Sulfur-containing aroma compounds are key contributors to the flavour of a diverse range of foods and beverages, such as wine. The tropical fruit characters of Sauvignon Blanc wines are attributed to the presence of the aromatic thiols 3-mercaptohexan-1-ol (3-MH), its acetate ester 3-mercaptohexyl acetate (3-MHA), and 4-mercapto-4-methylpentan-2-one (4-MMP). These aromatic thiols are not detectable in grape juice to any significant extent but are released by yeast during alcoholic fermentation. While the processes involved in the release of 3-MH and 4-MMP from their cysteinylated precursors have been studied extensively, degradation pathways for glutathione S-conjugates (GSH-3-MH and GSH-4-MMP) have not. In this study, a candidate gene approach was taken, focusing on genes known to play a role in glutathione and glutathione-S-conjugate turnover in Saccharomyces cerevisiae. Our results confirm the role of Opt1p as the major transporter responsible for uptake of GSH-3-MH and GSH-4-MMP, and identify vacuolar Ecm38p as a key determinant of 3-MH release from GSH-3-MH. ECM38 was unimportant, on the other hand, for release of 4-MMP, and abolition of vacuolar biogenesis caused an increase in the amount of 4-MMP released. The alternative cytosolic glutathione degradation pathway was not involved in release of either thiol from their glutathionylated precursors. Finally, cycling of GSH-3-MH and/or its breakdown intermediates between the cytosol and the vacuole or extracellular space was implicated in modulation of 3-MH formation. Together, these results provide new targets for development of yeast strains that optimize release of these potent volatile sulfur compounds, and further our understanding of the processes involved in glutathione-S-conjugate turnover.