UCD School of Biomolecular and Biomedical Science, Conway Institute, University College, Dublin 4, Ireland.
Amino Acids. 2012 Jan;42(1):199-205. doi: 10.1007/s00726-011-0864-8. Epub 2011 Mar 3.
Astrocyte cells require cysteine as a substrate for glutamate cysteine ligase (γ-glutamylcysteine synthase; EC 6.3.2.2) catalyst of the rate-limiting step of the γ-glutamylcycle leading to formation of glutathione (L: -γ-glutamyl-L: -cysteinyl-glycine; GSH). In both astrocytes and glioblastoma/astrocytoma cells, the majority of cysteine originates from reduction of cystine imported by the x (c) (-) cystine-glutamate exchanger. However, the transsulfuration pathway, which supplies cysteine from the indispensable amino acid, methionine, has recently been identified as a significant contributor to GSH synthesis in astrocytes. The purpose of this review is to evaluate the importance of the transsulfuration pathway in these cells, particularly in the context of a reserve pathway that channels methionine towards cysteine when the demand for glutathione is high, or under conditions in which the supply of cystine by the x (c) (-) exchanger may be compromised.
星形胶质细胞需要半胱氨酸作为谷氨酸半胱氨酸连接酶（γ-谷氨酰半胱氨酸合酶；EC 6.3.2.2）的底物，该酶是γ-谷氨酰循环限速步骤的催化剂，导致谷胱甘肽的形成（L：-γ-谷氨酰-L：-半胱氨酸-甘氨酸；GSH）。在星形胶质细胞和神经胶质瘤/星形细胞瘤细胞中，大部分半胱氨酸来源于通过 x（c）（-）胱氨酸-谷氨酸交换器导入的胱氨酸还原。然而，最近发现，转硫途径可以从必需氨基酸蛋氨酸供应半胱氨酸，这是星形胶质细胞中谷胱甘肽合成的重要贡献途径。本综述的目的是评估转硫途径在这些细胞中的重要性，特别是在当对谷胱甘肽的需求高时，或当 x（c）（-）交换器供应胱氨酸可能受损的情况下，该途径将蛋氨酸导向半胱氨酸的储备途径的背景下。
