FLUOROMETHYLENE DEOXYCYTIDINE DIPHOSPHATE(FMCDP) INHIBIT RIBONUCLEOTIDE REDUCTAS

(E)-2'-氟亚甲基-2'-脱氧胞苷5 '-二磷酸 （（E）-FMCDP），通过磷酸化临床上有前途的 抗肿瘤药物MDL 10 1，73 1是一种有效的时间依赖性灭活剂 的RNR。 EPR光谱显示，失活伴随着 损失Tyro和形成新的自由基物质。 9.4 GHz EPR 这个新自由基的光谱揭示了两个超精细分裂， 大约1.5mT，产生三重样信号。 孵育 [6 '-2H]（E）-FMCDP改变了EPR谱，为以下情况提供了证据： 由RDPR产生的基于核苷酸的自由基物质。 观察到的 信号是双重信号和三重信号的1：1复合， 后者与用未标记的抑制剂获得的相同。 在2 H2O中使用（E）-FMCDP的研究也产生这些的1：1混合物 两个激进的信号 这些同位素标记的结果 实验 建议约0.5当量氘在 6位，分别。 RNR与 [6 '-2H]-（E）-FMCDP仅产生该假设所导致的双峰 我们期待。 139.5 GHz EPR谱确立了 新自由基物种的g值。 模拟9.4和139.5 GHz EPR谱产生一组自洽的主超精细 价值观 自由基中间体被认为是由一个 基于底物的烯丙基。 拟议结构和 其形成的假设机制提供了进一步的支持， Y-氢原子引发催化假说 从核苷酸底物中提取。

(E)-2'-fluoromethylene-2'-deoxycytidine 5'-diphosphate ((E)-FMCDP), obtained by phosphorylation of the clinically promising anti-tumor agent MDL 10 1,73 1, is a potent time-dependent inactivator of RNR. EPR spectroscopy reveals that inactivation is accompanied by loss of Tyro and formation of a new radical species. The 9.4 GHz EPR spectrum of this new radical reveals two hyperfine splittings of approximately 1.5 mT, producing a triplet like signal. Incubation with [6'-2H](E)-FMCDP alters this EPR spectrum, providing evidence for a nucleotide based radical species generated by RDPR. The observed signal is a 1: 1 composite of a doublet and a triplet signal, the latter being identical to that obtained with unlabeled inhibitor. Studies with (E)-FMCDP in 2H20 also produce a 1: 1 mixture of these two radical signals. The results of these isotope labeling experiments suggest wash-out/in of -0.5 equivalents of deuterium at the 6-position, respectively. Incubation of RNR with [6'-2H]-(E)-FMCDP produced only the doublet as this hypothesis leads us to expect. 139.5 GHz EPR spectra established the principal g-values of the new radical species. Simulation of the 9.4 and 139.5 GHz EPR spectra yield a self-consistent set of principal hyperfine values. The radical intermediate is proposed to arise from a substrate based allyl radical. The proposed structure and a postulated mechanism for its formation provides further support for the hypothesis that catalysis is initiated by Y-hydrogen atom abstraction from the nucleotide substrate.