Tryptophan (Trp) is a proteinogenic aromatic amino acid; however, high levels of Trp are toxic in animals and yeast with unknown mechanisms. Previously, we suggested that aromatic aminotransferase Aro9 is important for excess Trp degradation. Besides, Schroeder and Ikui showed that aro9Δ is sensitive to membrane stress by sodium dodecyl sulfate. Therefore, Trp accumulation may reduce the cell wall or membrane (CW/M) stress tolerance through participation of cell wall integrity (CWI) pathway, which detects and responds to CW/M perturbations. In this study, we found that yeast mutants of the CWI mitogen-activated protein kinase cascade were susceptible to excess Trp. Also, the Trp degradation deficient mutant aro8Δ aro9Δ cells, in which Trp accumulation was confirmed, were sensitive to several CW/M stresses. These results indicated that accumulation of Trp is adverse for the CW/M stress resistance and may disturb appropriate signal transduction responding to the stress.

中文翻译：

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高水平的色氨酸会降低酿酒酵母细胞壁或膜的应激耐受性。


色氨酸 (Trp) 是一种蛋白质芳香氨基酸；然而，高浓度的色氨酸对动物和酵母具有毒性，其机制尚不清楚。之前，我们认为芳香族转氨酶 Aro9 对于过度的色氨酸降解很重要。此外，Schroeder 和 Ikui 表明 aro9Δ 对十二烷基硫酸钠的膜应激敏感。因此，Trp 积累可能通过参与细胞壁完整性 (CWI) 途径来降低细胞壁或膜 (CW/M) 应激耐受性，该途径检测并响应 CW/M 扰动。在这项研究中，我们发现 CWI 丝裂原激活蛋白激酶级联的酵母突变体对过量的色氨酸敏感。此外，Trp 降解缺陷突变体 aro8Δ aro9Δ 细胞（其中色氨酸积累得到证实）对几种 CW/M 胁迫敏感。这些结果表明，Trp 的积累不利于 CW/M 应激抵抗，并可能干扰响应应激的适当信号转导。