Tsukamoto I, Kojo S
Department of Food Science and Nutrition, Nara Women's University, Japan.
J Nutr Sci Vitaminol (Tokyo). 1990 Aug;36(4):357-63. doi: 10.3177/jnsv.36.4-supplementi_357.
Thymidylate synthase and thymidine kinase, which catalyze the formation of thymidylate via the de novo and salvage pathways, respectively, are rate-determining enzymes in DNA synthesis. The increases in the activities of hepatic thymidylate synthase and thymidine kinase were significantly suppressed at 24 h after 70% partial hepatectomy in rats that had been administered cycloheximide. Concomitantly, other regenerative parameters such as the liver weight and contents of protein, RNA, and DNA were also significantly reduced in 24-h regenerating liver of cycloheximide-treated rats. When actinomycin D was injected, the activity of thymidine kinase, the liver weight, and contents of protein, RNA, and DNA were completely depressed in 24-h regenerating liver. However, the activity of thymidylate synthase in actinomycin D-administered rats rose to the level similar to the control (70% partially hepatectomized). The immunoblotting assay showed that thymidylate synthase is newly synthesized during liver regeneration after partial hepatectomy without being affected with actinomycin D.
胸苷酸合成酶和胸苷激酶分别通过从头合成途径和补救途径催化胸苷酸的形成，它们是DNA合成中的限速酶。在给予环己酰亚胺的大鼠中，70%肝部分切除术后24小时，肝胸苷酸合成酶和胸苷激酶的活性增加受到显著抑制。同时，在环己酰亚胺处理大鼠的24小时再生肝中，其他再生参数如肝脏重量以及蛋白质、RNA和DNA的含量也显著降低。当注射放线菌素D时，24小时再生肝中胸苷激酶的活性、肝脏重量以及蛋白质、RNA和DNA的含量完全受到抑制。然而，给予放线菌素D的大鼠中胸苷酸合成酶的活性上升至与对照组（70%肝部分切除）相似的水平。免疫印迹分析表明，部分肝切除术后肝再生过程中胸苷酸合成酶是新合成的，且不受放线菌素D的影响。
