Kwon Yun Kyung, Lu Wenyun, Melamud Eugene, Khanam Nurussaba, Bognar Andrew, Rabinowitz Joshua D
Department of Chemistry and Lewis-Sigler Institute for Integrative Genomics, Carl Icahn Laboratory, Princeton University, Washington Road, Princeton, New Jersey 08544, USA.
Nat Chem Biol. 2008 Oct;4(10):602-8. doi: 10.1038/nchembio.108. Epub 2008 Aug 24.
Mass spectrometry technologies for measurement of cellular metabolism are opening new avenues to explore drug activity. Trimethoprim is an antibiotic that inhibits bacterial dihydrofolate reductase (DHFR). Kinetic flux profiling with (15)N-labeled ammonia in Escherichia coli reveals that trimethoprim leads to blockade not only of DHFR but also of another critical enzyme of folate metabolism: folylpoly-gamma-glutamate synthetase (FP-gamma-GS). Inhibition of FP-gamma-GS is not directly due to trimethoprim. Instead, it arises from accumulation of DHFR's substrate dihydrofolate, which we show is a potent FP-gamma-GS inhibitor. Thus, owing to the inherent connectivity of the metabolic network, falling DHFR activity leads to falling FP-gamma-GS activity in a domino-like cascade. This cascade results in complex folate dynamics, and its incorporation in a computational model of folate metabolism recapitulates the dynamics observed experimentally. These results highlight the potential for quantitative analysis of cellular metabolism to reveal mechanisms of drug action.
用于测量细胞代谢的质谱技术正在为探索药物活性开辟新途径。甲氧苄啶是一种抑制细菌二氢叶酸还原酶（DHFR）的抗生素。在大肠杆菌中使用（15）N标记的氨进行动力学通量分析表明，甲氧苄啶不仅导致DHFR的阻断，还导致叶酸代谢的另一种关键酶：叶酰聚γ-谷氨酸合成酶（FP-γ-GS）的阻断。FP-γ-GS的抑制并非直接由甲氧苄啶引起。相反，它源于DHFR底物二氢叶酸的积累，我们证明二氢叶酸是一种有效的FP-γ-GS抑制剂。因此，由于代谢网络的固有连通性，DHFR活性下降会导致FP-γ-GS活性以多米诺骨牌式的级联下降。这种级联导致复杂的叶酸动态变化，并且将其纳入叶酸代谢的计算模型中可重现实验观察到的动态变化。这些结果突出了细胞代谢定量分析揭示药物作用机制的潜力。
