gamma-Fluoromethotrexate: synthesis and biological activity of a potent inhibitor of dihydrofolate reductase with greatly diminished ability to form poly-gamma-glutamates.
gamma-Fluoromethotrexate: synthesis and biological activity of a potent inhibitor of dihydrofolate reductase with greatly diminished ability to form poly-gamma-glutamates.
复制标题
γ-氟甲氨蝶呤：二氢叶酸还原酶有效抑制剂的合成和生物活性，其形成聚γ-谷氨酸的能力大大降低。
DOI：
10.1073/pnas.82.9.2598
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发表时间：
1985
影响因子：
11.1
通讯作者：
Coward,JK
中科院分区：
文献类型：
--
作者：
Galivan,J;Inglese,J;McGuire,JJ;Nimec,Z;Coward,JK
合成了一种谷氨酸部分γ -碳上含氟的甲氨蝶呤（MTX）类似物γ -氟甲氨蝶呤（FMTX），并对其生化和药理学性质进行了评价。FMTX对几种来源的二氢叶酸还原酶的抑制作用与MTX所显示的几乎相同。最重要的是，FMTX是一种极差的叶酸聚（γ -谷氨酸）合成酶的底物，这种酶催化高度保留的细胞毒性MTX多谷氨酸的生物合成。在H35肝癌细胞中的摄取实验表明，FMTX的积累程度与稳态下的MTX大致相同。这两种衍生品的快速外流也非常相似。在细胞中检测到的两种化合物之间的主要区别是FMTX的谷氨酰化程度较低，这是由于与潜在酰胺形成羧基相邻的氟具有电负性。将分裂细胞暴露在50微米的MTX环境中2小时和6小时，每克细胞蛋白的多谷氨酸（超过两个谷氨酸残基）分别形成55和130 nmol。使用FMTX后，这些值分别降低了98%和93%。生长抑制研究表明，当细胞连续暴露于每种衍生物72小时时，MTX的毒性仅比FMTX高12倍。当曝光时间缩短时，观察到的抑制效果差异更大；对于2小时的脉冲，MTX比FMTX有效2300倍。这些数据与FMTX和MIX脉冲对完整细胞中胸苷酸生物合成的影响有关。结果表明，在所检测的参数中，FMTX从培养基中去除后毒性的大幅降低与谷氨酰化受损最相关。这些数据有力地表明，MTX的长期毒性是代谢转化为MTX多谷氨酸的结果，而且这些影响在短期内比长期暴露于抗叶酸盐中要显著得多。
A methotrexate (MTX) analog containing fluorine at the gamma-carbon of the glutamate moiety, gamma-fluoromethotrexate (FMTX), has been synthesized and evaluated for its biochemical and pharmacological properties. FMTX inhibition of dihydrofolate reductase from several sources is nearly equivalent to that shown by MTX. Most important, FMTX is an exceedingly poor substrate for folylpoly (gamma-glutamate) synthetase, the enzyme that catalyzes the biosynthesis of the highly-retained, cytotoxic MTX polyglutamates. Uptake experiments in H35 hepatoma cells show that FMTX accumulates to approximately the same extent as MTX at steady state. The rapid efflux of both derivatives is also very similar. The major difference detected in cells between the two compounds is the meager glutamylation of FMTX, due to the electronegative properties of the fluorine adjacent to the potential amide-forming carboxyl group. Exposure of dividing cells to 50 microM MTX for 2 and 6 hr results in the formation of 55 and 130 nmol, respectively, of the polyglutamates (more than two glutamate residues)/g of cell protein. With FMTX these values were reduced by 98% and 93%, respectively. Growth inhibition studies show that MTX is only 12-fold more toxic than FMTX when the cells are exposed to each derivative continuously for 72 hr. When the exposure time is reduced, a greater disparity between the inhibitory effects is observed; with a 2-hr pulse, MTX is 2300-fold more effective than FMTX. These data correlate with the effects of pulses of FMTX and MIX on de novo thymidylate biosynthesis in intact cells. The results indicate that of the parameters examined, the vastly reduced toxicity of FMTX after its removal from the culture medium is best correlated with impaired glutamylation. The data strongly suggest that prolonged toxicity of MTX is a result of metabolic conversion to MTX polyglutamates and that these effects are far more dramatic in short-term than in long-term exposure to the antifolates.