p-Hydroxymandelate oxidase (Hmo) is a flavin mononucleotide (FMN)-dependent enzyme that oxidizes mandelate to benzoylformate. How the FMN-dependent oxidation is executed by Hmo remains unclear at the molecular level. A continuum of snapshots from crystal structures of Hmo and its mutants in complex with physiological/nonphysiological substrates, products and inhibitors provides a rationale for its substrate enantioselectivity/promiscuity, its active-site geometry/reactivity and its direct hydride-transfer mechanism. A single mutant, Y128F, that extends the two-electron oxidation reaction to a four-electron oxidative decarboxylation reaction was unexpectedly observed. Biochemical and structural approaches, including biochemistry, kinetics, stable isotope labeling and X-ray crystallography, were exploited to reach these conclusions and provide additional insights.

中文翻译：

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α-羟基酸氧化酶的生化和结构探索揭示了四电子氧化脱羧反应。

对羟基扁桃酸氧化酶 (Hmo) 是一种黄素单核苷酸 (FMN) 依赖性酶，可将扁桃酸氧化为苯甲酰甲酸。Hmo 如何执行依赖 FMN 的氧化在分子水平上仍不清楚。来自 Hmo 及其突变体与生理/非生理底物、产物和抑制剂复合物的晶体结构的连续快照为其底物对映选择性/杂乱性、活性位点几何形状/反应性及其直接氢化物转移机制提供了基本原理。出人意料地观察到一个单一的突变体 Y128F，它将两电子氧化反应扩展到四电子氧化脱羧反应。生化和结构方法，包括生物化学、动力学、稳定同位素标记和 X 射线晶体学，