title: Nitrogen regulation involved in the accumulation of urea in Saccharomyces cerevisiae.
abstract: Rice wine is a popular traditional alcoholic drink with a long history in China. However, the presence of the potential carcinogen ethyl carbamate (EC) raises a series of food safety concerns. Although the metabolic pathway of urea (the major precusor of EC) has been characterized in Saccharomyces cerevisiae, the regulation of urea accumulation remains unclear, making the efficient elimination of urea difficult. To demonstrate the regulatory mechanisms governing urea accumulation, three key nitrogen sources that can inhibit urea utilization for a commercial S. cerevisiae strain were identified. In addition, regulators of nitrogen catabolite repression (NCR) and target of rapamycin (TOR) pathways were identified as being involved in urea accumulation by real-time quantitative PCR. Based on these results, preferred nitrogen sources were found to repress urea utilization by converting them to glutamine or glutamate. Moreover, the results indicated that the manner of urea metabolism regulation was different for two positive regulators involved in NCR; Gln3p can be retained in the cytoplasm by glutamine, while Gat1p can be retained by glutamine and glutamate. Furthermore, this was confirmed by fluorescence location detection. These new findings provide new targets for eliminating EC and other harmful nitrogen-containing compounds in fermented foods.
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu, People's Republic of China.
authors.forename: Xinrui
authors.initials: X
authors.lastname: Zhao
authors.forename: Huijun
authors.initials: H
authors.lastname: Zou
authors.forename: Jianwei
authors.initials: J
authors.lastname: Fu
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Jingwen
authors.initials: J
authors.lastname: Zhou
authors.forename: Guocheng
authors.initials: G
authors.lastname: Du
mesh_terms: D057465:Catabolite Repression; D015966:Gene Expression Regulation, Fungal; D009584:Nitrogen / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D014508:Urea / Q000378:metabolism*
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D014508:Urea; D009584:Nitrogen
keywords: TOR pathway; ethyl carbamate; fluorescence location detection; nitrogen catabolite repression; rice wine