DL-threo-4-fluoroglutamic acid. A chain-terminating inhibitor of folylpolyglutamate synthesis.
DL-threo-4-fluoroglutamic acid. A chain-terminating inhibitor of folylpolyglutamate synthesis.
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DOI：
10.1016/s0021-9258(18)88843-3
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发表时间：
1985-06
期刊：
影响因子：
--
通讯作者：
J. McGuire;J. Coward
中科院分区：
文献类型：
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作者：
J. McGuire;J. Coward
研究了4-氟谷氨酸对部分纯化的大鼠肝叶酰聚谷氨酸合成酶催化反应的影响。 DL-threo-4-Fluoroglutamate 是一种有效的、浓度依赖性的四氢叶酸和甲氨蝶呤多谷氨酰化抑制剂，而赤型异构体的抑制作用很弱。 4-氟谷氨酸作为替代底物； DL-苏型异构体的掺入效率仅略低于L-谷氨酸，而赤型异构体的掺入效果较差。所得产物，蝶酰谷氨酰-γ-(4-氟)谷氨酸，是进一步谷氨酰化的非常差的底物。因此，当四氢叶酸和 4-氟谷氨酸盐为底物时，唯一的 Zn/HCl 裂解产物与化学合成的对氨基苯甲酰谷氨酰基-γ-(4-氟)谷氨酸盐在高效液相色谱上进行共色谱分析。以[3H]甲氨蝶呤(4-NH2-10-CH3PteGlu)和4-氟谷氨酸为底物，与化学合成的4-NH2-CH3PteGlu-γ-(4-氟)谷氨酸进行高效液相色谱共层析，得到一种产物。 γ-谷氨酰水解酶消化实验和定量氨基酸分析进一步证明[3H]甲氨蝶呤的产物是二肽。仅在强制条件下才会出现痕量产物，该产物具有与添加第二个4-氟谷氨酸盐一致的性质。化学和酶法合成的含氟谷氨酸产物作为大鼠肝叶酰聚谷氨酸合成酶的底物，其性能比类似的二谷氨酰化合物低至少 15 倍。这些结果与 4-氟谷氨酸通过“泄漏”链终止机制抑制聚谷氨酸合成一致。
The effects of 4-fluoroglutamate on the reaction catalyzed by partially purified rat liver folylpolyglutamate synthetase have been investigated. DL-threo-4-Fluoroglutamate was an effective, concentration-dependent inhibitor of polyglutamylation of both tetrahydrofolate and methotrexate, while the erythro isomer was weakly inhibitory. 4-Fluoroglutamate acted as an alternate substrate; the DL-threo isomer was incorporated only slightly less effectively than L-glutamate, while the erythro isomer was poorly incorporated. The resulting product, a pteroylglutamyl-gamma-(4-fluoro)glutamate, was a very poor substrate for further glutamylation. Thus, when tetrahydrofolate and 4-fluoroglutamate were substrates, the sole Zn/HCl cleavage product co-chromatographed on high performance liquid chromatography with chemically synthesized p-aminobenzoylglutamyl-gamma-(4-fluoro)glutamate. When [3H]methotrexate (4-NH2-10-CH3PteGlu) and 4-fluoroglutamate were the substrates, one product was obtained which co-chromatographed on high performance liquid chromatography with chemically synthesized 4-NH2-CH3PteGlu-gamma-(4-fluoro)glutamate. Further evidence that the product from [3H]methotrexate was a dipeptide came from gamma-glutamyl hydrolase digestion experiments and quantitative amino acid analysis. The appearance of trace amounts of a product having properties consistent with the addition of a second 4-fluoroglutamate occurred only under forcing conditions. The chemically and enzymatically synthesized fluoroglutamate-containing products were at least 15 times poorer than the analogous diglutamyl compound as substrates for rat liver folylpolyglutamate synthetase. These results are consistent with inhibition of polyglutamate synthesis by 4-fluoroglutamate through a “leaky” chain termination mechanism.