Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA.
J Biol Inorg Chem. 2024 Apr;29(3):291-301. doi: 10.1007/s00775-024-02051-3. Epub 2024 May 9.
In addition to its primary oxygen-atom-transfer function, cysteamine dioxygenase (ADO) exhibits a relatively understudied anaerobic disproportionation reaction (ADO-Fe(III)-SR → ADO-Fe(II) + ½ RSSR) with its native substrates. Inspired by ADO disproportionation reactivity, we employ [Fe(tacn)Cl] (tacn = 1,4,7-triazacyclononane) as a precursor for generating Fe(III)-thiolate model complexes in buffered aqueous media. A series of Fe(III)-thiolate model complexes are generated in situ using aqueous [Fe(tacn)Cl] and thiol-containing ligands cysteamine, penicillamine, mercaptopropionate, cysteine, cysteine methyl ester, N-acetylcysteine, and N-acetylcysteine methyl ester. We observe trends in UV-Vis and electron paramagnetic resonance (EPR) spectra, disproportionation rate constants, and cathodic peak potentials as a function of thiol ligand. These trends will be useful in rationalizing substrate-dependent Fe(III)-thiolate disproportionation reactions in metalloenzymes.
除了其主要的氧原子转移功能外，半胱氨酸双加氧酶（ADO）还表现出相对未被充分研究的厌氧歧化反应（ADO-Fe(III)-SR → ADO-Fe(II) + ½ RSSR），其天然底物也是如此。受 ADO 歧化反应活性的启发，我们使用 [Fe(tacn)Cl]（tacn = 1,4,7-三氮杂环壬烷）作为前体，在缓冲水溶液介质中生成 Fe(III)-硫醇模型配合物。使用水溶液中的 [Fe(tacn)Cl] 和含巯基的配体半胱氨酸、青霉素胺、巯基丙酸、半胱氨酸、半胱氨酸甲酯、N-乙酰半胱氨酸和 N-乙酰半胱氨酸甲酯，在原位生成一系列 Fe(III)-硫醇模型配合物。我们观察到随着巯基配体的变化，紫外可见光谱和电子顺磁共振（EPR）光谱、歧化反应速率常数和阴极峰电位的趋势。这些趋势将有助于合理推断金属酶中依赖于底物的 Fe(III)-硫醇歧化反应。
