Das P, Das S R, Moorji A, Baer H P
Department of Microbiology, National Institute of Cholera and Enteric Diseases, Calcutta, India.
Parasitol Res. 1997;83(4):364-9. doi: 10.1007/s004360050263.
The uptake and transportation of purine and pyrimidine based nucleosides by trophozoites of axenically grown Entamoeba histolytica (HMI-IMSS) were studied. The trophozoites transported adenosine and its analog tubercidin (1 microM) at a significant rate but poor transportation was observed in case of uridine (about 10% relative rate), inosine (3%), thymidine (2%) and formycin B (1%). The Km for adenosine was 160 +/- 42 microM. Unlabeled nucleosides (100 microM) inhibited adenosine and tubercidin transport. Adenosine related compounds 5'-deoxyadenosine and nebularin inhibited adenosine and tubercidine transport by 50% or more. However, inosine related compounds guanosine, 3'-deoxyinosine and formycin B were less inhibitory. The pyrimidine nucleosides uridine, thymidine and cytidine were poorly inhibitory. 6-[(4 nitrobenzyl)-mercapto] purine ribonucleoside, an inhibitor of mammalian nucleoside transporter, inhibited adenosine or tubercidin transport in E. histolytica variably between 0-30% at 10 microM, but dilazep, a known inhibitor, was inactive upto 10 microM. Increase in temperature from 22 degrees C to 33 degrees C enhanced the rate of transport of adenosine 4.5 fold, tubercidin 7.3 fold and of inosine 4 fold. These findings along with the structure activity figures suggested that transport was mediated and not passive.
研究了无菌培养的溶组织内阿米巴（HMI-IMSS）滋养体对嘌呤和嘧啶类核苷的摄取和转运。滋养体以显著速率转运腺苷及其类似物杀结核菌素（1微摩尔），但尿苷（相对速率约10%）、肌苷（3%）、胸苷（2%）和间型霉素B（1%）的转运较差。腺苷的米氏常数为160±42微摩尔。未标记的核苷（100微摩尔）抑制腺苷和杀结核菌素的转运。腺苷相关化合物5'-脱氧腺苷和星状菌素抑制腺苷和杀结核菌素的转运达50%或更多。然而，肌苷相关化合物鸟苷、3'-脱氧肌苷和间型霉素B的抑制作用较小。嘧啶核苷尿苷、胸苷和胞苷的抑制作用较弱。6-[(4-硝基苄基)-巯基]嘌呤核糖核苷是一种哺乳动物核苷转运体抑制剂，在10微摩尔时对溶组织内阿米巴的腺苷或杀结核菌素转运的抑制率在0-30%之间变化，但已知抑制剂地拉卓在10微摩尔时无活性。温度从22℃升高到33℃使腺苷的转运速率提高了4.5倍，杀结核菌素提高了7.3倍，肌苷提高了4倍。这些发现以及构效关系表明转运是由介导的而非被动的。
