Taniguchi Misako, Mori Nobuko, Iramina Chizuru, Yasutake Akira
Department of Nutrition Sciences, Nakamura Gakuen University, Fukuoka 814-0198, Japan.
Department of Biomedical Laboratory Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto 862-0976, Japan.
ScientificWorldJournal. 2016;2016:6382467. doi: 10.1155/2016/6382467. Epub 2016 Aug 15.
Weanling male Wistar rats were fed on a 10% soybean protein isolate (SPI) diet for 3 weeks with or without supplementing 0.3% sulfur-containing amino acids (SAA; methionine or cystine) to examine relationship between glutathione (GSH) levels and activities of NADPH-producing enzymes, glucose 6-phosphate dehydrogenase (G6PD) and malic enzyme (ME), in the liver. Of rats on the 10% SPI diet, GSH levels were lower and the enzyme activities were higher than of those fed on an SAA-supplemented diet. Despite the lower GSH level, γ-glutamylcysteine synthetase (γ-GCS) activity was higher in the 10% SPI group than other groups. Examination of mRNAs of G6PD and ME suggested that the GSH-suppressing effect on enzyme induction occurred prior to and/or at transcriptional levels. Gel electrophoresis of G6PD indicated that low GSH status caused a decrease in reduced form and an increase in oxidized form of the enzyme, suggesting an accelerated turnover rate of the enzyme. In primary cultured hepatocytes, insulin response to induce G6PD activity was augmented in low GSH levels manipulated in the presence of buthionine sulfoximine. These findings indicated that elevation of the G6PD activity in low GSH levels was caused by amplified insulin response for expression of the enzyme and accelerated turnover rate of the enzyme molecule.
将断乳雄性Wistar大鼠用含10%大豆分离蛋白（SPI）的饲料喂养3周，饲料中添加或不添加0.3%含硫氨基酸（SAA；蛋氨酸或胱氨酸），以研究肝脏中谷胱甘肽（GSH）水平与产生NADPH的酶（葡萄糖6-磷酸脱氢酶（G6PD）和苹果酸酶（ME））活性之间的关系。在食用10%SPI饲料的大鼠中，GSH水平较低，酶活性高于食用添加SAA饲料的大鼠。尽管GSH水平较低，但10%SPI组的γ-谷氨酰半胱氨酸合成酶（γ-GCS）活性高于其他组。对G6PD和ME的mRNA进行检测表明，GSH对酶诱导的抑制作用发生在转录水平之前和/或转录水平。G6PD的凝胶电泳表明，低GSH状态导致该酶的还原形式减少，氧化形式增加，这表明该酶的周转速率加快。在原代培养的肝细胞中，在丁硫氨酸亚砜胺存在的情况下，低GSH水平增强了胰岛素诱导G6PD活性的反应。这些发现表明，低GSH水平时G6PD活性的升高是由胰岛素对该酶表达的反应增强以及酶分子周转速率加快所致。
