Hosaka K, Yamashita S
J Bacteriol. 1980 Jul;143(1):176-81. doi: 10.1128/jb.143.1.176-181.1980.
Choline transport of Saccharomyces cerevisiae was measured by the filtration method with the use of glass microfiber paper. The uptake was time and temperature dependent. The kinetics of choline transport showed Michaelis behavior; an appearent Km for choline was 0.56 microM. N-Methylethanolamine, N,N-dimethylethanolamine, and beta-methylcholine were competitive inhibitors of choline transport, with Ki values of 40.1, 3.1, and 6.9 microM, respectively. Ethanolamine, phosphorylcholine, and various amino acids examined had no effect. Choline transport required metabolic energy; removal of glucose resulted in a great loss of transport activity, and the remaining activity was abolished by 2,4-dinitrophenol, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, arsenate, and cyanide. External Na+ was not required, and the transport was not effected by ionophores, valinomycin, and gramicidin D. These results indicate that S. cerevisiae possess an active choline transport system mediated by a specific carrier. This view is further supported by the isolation and characterization of a choline transport mutant. The choline transport activity in this mutant was very low, whereas the transport of L-leucine, L-methionine, D-glucose, and myo-inositol was normal. Together with the choline transport mutant, mutants defective in choline kinase were also isolated.
利用玻璃微纤维滤纸通过过滤法测定了酿酒酵母的胆碱转运。摄取量与时间和温度有关。胆碱转运动力学表现出米氏行为；胆碱的表观 Km 为 0.56 μM。N-甲基乙醇胺、N,N-二甲基乙醇胺和β-甲基胆碱是胆碱转运的竞争性抑制剂，Ki 值分别为 40.1、3.1 和 6.9 μM。所检测的乙醇胺、磷酸胆碱和各种氨基酸均无影响。胆碱转运需要代谢能量；去除葡萄糖会导致转运活性大幅丧失，剩余活性会被 2,4-二硝基苯酚、羰基氰化物对三氟甲氧基苯基腙、砷酸盐和氰化物消除。不需要外部 Na+，转运不受离子载体、缬氨霉素和短杆菌肽 D 的影响。这些结果表明酿酒酵母拥有一个由特定载体介导的活性胆碱转运系统。胆碱转运突变体的分离和表征进一步支持了这一观点。该突变体中的胆碱转运活性非常低，而 L-亮氨酸、L-甲硫氨酸、D-葡萄糖和肌醇的转运正常。与胆碱转运突变体一起，还分离出了胆碱激酶缺陷的突变体。
