Ohta J, Kwon Y H, Stipanuk M H
Department of Biochemistry, Okayama University Medical School, Japan.
Amino Acids. 2000;19(3-4):705-28. doi: 10.1007/s007260070017.
Hepatocytes were cultured for 3 days as spheroids (aggregates) or as monolayers in basal medium and in sulfur amino acid-supplemented media. Cultured hepatocytes had low levels of cysteine dioxygenase (CDO) activity and normal levels of gamma-glutamylcysteine synthetase (GCS) and cysteine-sulfinate decarboxylase (CSDC) activities compared to freshly isolated cells. CDO activity increased and GCS activity decreased in a dose-response manner in cells cultured in either methionine- or cysteine-supplemented media. CSDC activity was not significantly affected by methionine supplementation. Changes in CDO and GCS were associated with changes in cysteine catabolism to taurine plus sulfate and in synthesis of glutathione, respectively. These responses are similar to those observed in liver of intact rats fed diets supplemented with sulfur amino acids. A near-maximal response of CDO or GCS activity was observed when the medium contained 1.O mmol/L of methionine plus cyst(e)ine. Changes in CDO and GCS activities did not appear to be mediated by changes in the intracellular glutathione concentration. Cultured hepatocytes offer a useful model for further studies of cysteine metabolism and its regulation in response to sulfur amino acid availability.
将肝细胞以球体（聚集体）形式或单层形式在基础培养基以及补充了含硫氨基酸的培养基中培养3天。与新鲜分离的细胞相比，培养的肝细胞中半胱氨酸双加氧酶（CDO）活性较低，而γ-谷氨酰半胱氨酸合成酶（GCS）和半胱氨酸亚磺酸脱羧酶（CSDC）活性正常。在补充了甲硫氨酸或半胱氨酸的培养基中培养的细胞中，CDO活性呈剂量反应性增加，而GCS活性呈剂量反应性降低。补充甲硫氨酸对CSDC活性没有显著影响。CDO和GCS的变化分别与半胱氨酸分解代谢为牛磺酸加硫酸盐以及谷胱甘肽合成的变化有关。这些反应与在喂食补充了含硫氨基酸饲料的完整大鼠肝脏中观察到的反应相似。当培养基中含有1.0 mmol/L的甲硫氨酸加半胱氨酸（或半胱氨酸）时，观察到CDO或GCS活性接近最大反应。CDO和GCS活性的变化似乎不是由细胞内谷胱甘肽浓度的变化介导的。培养的肝细胞为进一步研究半胱氨酸代谢及其对含硫氨基酸可用性的调节提供了一个有用的模型。
