title: The IRC7 gene encodes cysteine desulphydrase activity and confers on yeast the ability to grow on cysteine as a nitrogen source.
abstract: Although cysteine desulphydrase activity has been purified and characterized from Saccharomyces cerevisiae, the gene encoding this activity in vivo has never been defined. We show that the full-length IRC7 gene, encoded by the YFR055W open reading frame, encodes a protein with cysteine desulphydrase activity. Irc7p purified to homogeneity is able to utilize l-cysteine as a substrate, producing pyruvate and hydrogen sulphide as products of the reaction. Purified Irc7p also utilized l-cystine and some other cysteine conjugates, but not l-cystathionine or l-methionine, as substrates. We further show that, in vivo, the IRC7 gene is both necessary and sufficient for yeast to grow on l-cysteine as a nitrogen source, and that overexpression of the gene results in increased H2 S production. Strains overexpressing IRC7 are also hypersensitive to a toxic analogue, S-ethyl-l-cysteine. While IRC7 has been identified as playing a critical role in converting cysteine conjugates to volatile thiols that are important in wine aroma, its biological role in yeast cells is likely to involve regulation of cysteine and redox homeostasis.
authors: Wine Science Group, School of Biological Sciences, University of Auckland, New Zealand.
authors: Margarita
authors: M
authors: Santiago
authors: Wine Science Group, School of Biological Sciences, University of Auckland, New Zealand.
authors: Richard C
authors: RC
authors: Gardner
mesh_terms: D003470:Culture Media / Q000737:chemistry; D003542:Cystathionine gamma-Lyase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism*; D006862:Hydrogen Sulfide / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D003470:Culture Media; D029701:Saccharomyces cerevisiae Proteins; D019289:Pyruvic Acid; D003542:Cystathionine gamma-Lyase; D003545:Cysteine; D009584:Nitrogen; D006862:Hydrogen Sulfide
keywords: Saccharomyces cerevisiae; aminotransferase; cystathionine β-lyase; cysteine homeostasis; hydrogen sulphide; varietal thiols