Barouki R, Chobert M N, Finidori J, Aggerbeck M, Nalpas B, Hanoune J
Hepatology. 1983 May-Jun;3(3):323-9. doi: 10.1002/hep.1840030308.
The clone C2 derived from a rat hepatoma cell line was used to investigate the mechanism of the induction of gamma-glutamyltransferase by ethanol. gamma-glutamyltransferase activity was detected in the C2 cell (1.4 mU per mg protein), and its kinetic properties were similar to normal rat liver gamma-glutamyltransferase. Ethanol provoked a dose- and time-dependent increase in gamma-glutamyltransferase activity, the maximum (2- to 3-fold) occurring 48 hr after the addition of ethanol (180 mM). In contrast, the activity of five other enzymes tested were not markedly modified by ethanol. Propanol was more potent than ethanol in inducing gamma-glutamyltransferase (5-fold stimulation), whereas methanol had no effect. The release of the enzyme in the medium was increased by ethanol and propanol. Several observations argue in favor of an increase in the biosynthesis of gamma-glutamyltransferase after ethanol addition: (i) ethanol increased the maximal velocity of the enzyme and did not modify the affinity for its substrates. It did not alter gamma-glutamyltransferase subcellular distribution; (ii) ethanol had no immediate effect when added directly to the assay mixture; (iii) the lag period and the time course of the increase in gamma-glutamyltransferase activity were those expected for an induction process; (iv) the increase in gamma-glutamyltransferase activity was prevented by cycloheximide and actinomycin D suggesting that ethanol acted at the transcriptional level. The effect of ethanol was not mimicked by acetaldehyde. In conclusion, we have demonstrated that ethanol increases the biosynthesis of gamma-glutamyltransferase in a rat hepatoma cell line which provides a new in vitro system.
从大鼠肝癌细胞系衍生而来的克隆C2用于研究乙醇诱导γ-谷氨酰转移酶的机制。在C2细胞中检测到γ-谷氨酰转移酶活性（每毫克蛋白质1.4毫微单位），其动力学特性与正常大鼠肝脏γ-谷氨酰转移酶相似。乙醇引起γ-谷氨酰转移酶活性呈剂量和时间依赖性增加，在加入乙醇（180 mM）后48小时达到最大值（增加2至3倍）。相比之下，所检测的其他五种酶的活性未被乙醇显著改变。丙醇在诱导γ-谷氨酰转移酶方面比乙醇更有效（刺激5倍），而甲醇没有作用。乙醇和丙醇增加了酶在培养基中的释放。几项观察结果支持乙醇添加后γ-谷氨酰转移酶生物合成增加的观点：（i）乙醇增加了酶的最大反应速度，且未改变对其底物的亲和力。它没有改变γ-谷氨酰转移酶的亚细胞分布；（ii）直接添加到测定混合物中时，乙醇没有立即产生作用；（iii）γ-谷氨酰转移酶活性增加的滞后期和时间进程是诱导过程所预期的；（iv）环己酰亚胺和放线菌素D可阻止γ-谷氨酰转移酶活性增加，这表明乙醇作用于转录水平。乙醛不能模拟乙醇的作用。总之，我们已经证明乙醇增加了大鼠肝癌细胞系中γ-谷氨酰转移酶的生物合成，这提供了一个新的体外系统。
