The transport of pteridines in CCRF-CEM human lymphoblastic cells.
The transport of pteridines in CCRF-CEM human lymphoblastic cells.
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CCRF-CEM 人淋巴母细胞中蝶啶的转运。
DOI：
10.1007/bf00292405
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发表时间：
1989
影响因子：
3
通讯作者：
Nazarbaghi,R
中科院分区：
文献类型：
--
作者：
Webber,S;Nazarbaghi,R
使用 [3H]6-羟基甲基蝶呤作为模型化合物，分析了 CCRF-CEM 人类淋巴母细胞用于未结合蝶啶流入和流出的转运途径。流入的机制表现出每毫克细胞蛋白的 Kmof 66.7 μM 和 Vmax 0.077 nmol/min。该过程对代谢抑制剂，特别是氧化磷酸化解偶联剂有些敏感，并且受到细胞外介质中其他蝶啶存在的显着影响。结果表明，Ki 值在 25 至 77 μM 之间的无 6-取代基（蝶呤）或在该位置具有甲基、羟基或甲酰基的蝶呤可能具有相同的摄取途径。 6-羧基蝶呤对系统的亲和力较低 (Ki>500 μM)，7-取代和 6,7-二取代衍生物以及 6 位上具有较大基团的化合物也是如此，例如新蝶呤和生物蝶呤 (Ki= 250–300 μM)。 [3H]6-羟甲基蝶呤的外流发生得很快，并且可以通过至少两条途径进行。第一个约占总流出量的 50%，被细胞外蝶呤抑制，并且在其对代谢抑制剂的敏感性模式和对蝶啶结构的特异性方面表现出与摄取系统相似的特性。剩余流出发生的途径对代谢抑制相对不敏感。腺嘌呤显着抑制 6-羟甲基蝶呤流入和流出（吸收的 Ki=10.6 μM），但似乎不共享相同的运输系统。类似地，甲氨蝶呤和叶酸对未结合的蝶啶转运途径表现出很小的亲和力。
The transport routes used by CCRF-CEM human lymphoblastoid cells for the influx and efflux of unconjugated pteridines were analyzed using [3H]6-hydroxy-methylpterin as a model compound. Influx proceeds by a mechanism that exhibits a Kmof 66.7 μMand a Vmaxof 0.077 nmol/min per mg cellular protein. The process is somewhat sensitive to metabolic inhibitors, particularly uncouplers of oxidative phosphorylation, and is significantly affected by the presence of other pteridines in the extracellular medium. The results suggest that pterins with either no 6-substituent (pterin) or those with methyl, hydroxyl, or formyl groups in this position, which exhibit Kivalues between 25 and 77 μM, may share the same pathway for uptake. 6-Carboxypterin exhibits low affinity for the system (Ki>500 μM), as do 7-substituted and 6,7-disubstituted derivatives and compounds with larger groups at the 6-position, such as neopterin and biopterin (Ki= 250–300 μM). Efflux of [3H]6-hydroxymethylpterin occurs rapidly and can proceed by at least two routes. The first, comprising approximately 50% of total efflux, is inhibited by extracellular pterins and exhibits similar properties to the uptake system in both its pattern of sensitivity to metabolic inhibitors and its specificity for pteridine structure. The route by which the remaining efflux occurs is relatively insensitive to metabolic inhibition. Adenine significantly inhibits 6-hydroxymethylpterin influx and efflux (Ki=10.6 μMfor uptake) but does not appear to share the same transport system. Similarly, methotrexate and folic acid exhibit little affinity for the unconjugated pteridine transport routes.