Ornithine decarboxylase (ODC) is the rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are oncometabolites that are required for proliferation, and pharmaceutical ODC inhibition is pursued for the treatment of hyperproliferative diseases, including cancer and infectious diseases. The most potent ODC inhibitor is 1-amino-oxy-3-aminopropane (APA). A previous crystal structure of an ODC–APA complex indicated that APA non-covalently binds ODC and its cofactor pyridoxal 5-phosphate (PLP) and functions by competing with the ODC substrate ornithine for binding to the catalytic site. We have revisited the mechanism of APA binding and ODC inhibition through a new crystal structure of APA-bound ODC, which we solved at 2.49 Å resolution. The structure unambiguously shows the presence of a covalent oxime between APA and PLP in the catalytic site, which we confirmed in solution by mass spectrometry. The stable oxime makes extensive interactions with ODC but cannot be catabolized, explaining APA's high potency in ODC inhibition. In addition, we solved an ODC/PLP complex structure with citrate bound at the substrate-binding pocket. These two structures provide new structural scaffolds for developing more efficient pharmaceutical ODC inhibitors.

中文翻译：

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1-氨基-氧-3-氨基丙烷结合和抑制鸟氨酸脱羧酶的结构基础

鸟氨酸脱羧酶 (ODC) 是多胺 (PA) 合成的限速酶。PA 是增殖所需的肿瘤代谢物，药物 ODC 抑制被用于治疗过度增殖性疾病，包括癌症和传染病。最有效的 ODC 抑制剂是 1-amino-oxy-3-aminopropane (APA)。ODC-APA 复合物的先前晶体结构表明 APA 非共价结合 ODC 及其辅因子吡哆醛 5-磷酸 (PLP)，并通过与 ODC 底物鸟氨酸竞争结合催化位点来发挥作用。我们通过 APA 结合的 ODC 的新晶体结构重新审视了 APA 结合和 ODC 抑制的机制，我们以 2.49 Å 的分辨率解决了这个问题。该结构明确表明催化位点中 APA 和 PLP 之间存在共价肟，我们通过质谱法在溶液中证实了这一点。稳定的肟与 ODC 发生广泛的相互作用但不能被分解代谢，这解释了 APA 在 ODC 抑制中的高效能。此外，我们解决了一个 ODC/PLP 复合结构，柠檬酸盐结合在底物结合袋中。这两种结构为开发更有效的药物 ODC 抑制剂提供了新的结构支架。