Kučera Igor, Sedláček Vojtěch
Department of Biochemistry, Faculty of Science, Masaryk University, Kotlářská 267/2, 61137, Brno, Czech Republic.
Biometals. 2025 Apr 16. doi: 10.1007/s10534-025-00685-7.
Phenylarsonic acid is the parent compound of a group of derivatives that occur as anthropogenic environmental contaminants in both less toxic As(V) and much more toxic As(III) redox states. To elucidate the mechanisms underlying their enzymatic redox conversions, the activities of two flavin reductases, ArsH and FerA, from the soil bacterium Paracoccus denitrificans were compared. The stopped-flow data demonstrated that PhAs(V) oxidized dihydroflavin mononucleotide bound to ArsH, but not to FerA. This result proves that ArsH has some substrate specificity for organoarsenic compounds. Under aerobic conditions, both enzymes accelerated the oxidation of PhAs(III) in a catalase-sensitive manner, indicating that hydrogen peroxide acts as an intermediate. HO was shown to react with PhAs(III) in a bimolecular (1:1) irreversible reaction. When exposed to blue light, flavin alone mediated rapid oxidation of PhAs(III) by O. Photooxidation by flavin acted in concert with chemical oxidation by transiently accumulating HO. The described processes may be relevant in the context of arsenic ecotoxicology and remediation.
苯胂酸是一组衍生物的母体化合物，这些衍生物作为人为环境污染物以毒性较小的五价砷（As(V)）和毒性大得多的三价砷（As(III)）氧化还原态存在。为了阐明其酶促氧化还原转化的潜在机制，比较了土壤反硝化副球菌中两种黄素还原酶ArsH和FerA的活性。停流数据表明，五价苯胂酸（PhAs(V)）氧化与ArsH结合的二氢黄素单核苷酸，但不氧化与FerA结合的二氢黄素单核苷酸。这一结果证明ArsH对有机砷化合物具有一定的底物特异性。在有氧条件下，两种酶均以过氧化氢酶敏感的方式加速了三价苯胂酸（PhAs(III)）的氧化，表明过氧化氢作为中间体起作用。已证明羟基自由基（HO）与PhAs(III)发生双分子（1:1）不可逆反应。当暴露于蓝光下时，黄素单独介导了O对PhAs(III)的快速氧化。黄素的光氧化与通过瞬时积累的HO进行的化学氧化协同作用。所述过程可能与砷的生态毒理学和修复有关。
