The dimethyl sulfone monooxygenase system is a two-component flavoprotein, catalyzing the monooxygenation of dimethyl sulfone (DMSO₂) by oxidative cleavage producing methanesulfinate and formaldehyde. The reductase component (DMSR) is a flavoprotein with FMN as a cofactor, catalyzing flavin reduction using NADH. The monooxygenase (DMSMO) uses reduced flavin from the reductase and oxygen for substrate monooxygenation. DMSMO can bind to FMN and FMNH⁻ with a K_d of 17.4 ± 0.9 μm and 4.08 ± 0.8 μm, respectively. The binding of FMN to DMSMO is required prior to binding DMSO₂. This also applies to the fast binding of reduced FMN to DMSMO followed by DMSO₂. Substituting reduced DMSR with FMNH⁻ demonstrated the same oxidation kinetics, indicating that FMNH⁻ from DMSR was transferred to DMSMO. The oxidation of FMNH⁻:DMSMO, with and without DMSO₂ did not generate any flavin adducts for monooxygenation. Therefore, H₂O₂ is likely to be the reactive agent to attack the substrate. The H₂O₂ assay results demonstrated production of H₂O₂ from the oxidation of FMNH⁻:DMSMO, whereas H₂O₂ was not detected in the presence of DMSO₂, confirming H₂O₂ utilization. The rate constant for methanesulfinate formation determined from rapid quenched flow and the rate constant for flavin oxidation were similar, indicating that H₂O₂ rapidly reacts with DMSO₂, with flavin oxidation as the rate-limiting step. This is the first report of the kinetic mechanisms of both components using rapid kinetics and of a method for methanesulfinate detection using LC–MS.

中文翻译：

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双组分黄素蛋白二甲基砜单加氧酶系统的反应机制和动力学：使用过氧化氢进行单加氧和底物裂解

二甲基砜单加氧酶系统是一种双组分黄素蛋白，通过氧化裂解催化二甲基砜(DMSO ₂ )的单加氧，产生甲亚磺酸盐和甲醛。还原酶成分 (DMSR) 是一种黄素蛋白，以 FMN 作为辅助因子，利用 NADH 催化黄素还原。单加氧酶 (DMSMO) 使用还原酶中的还原黄素和氧气进行底物单加氧。DMSMO 可以与 FMN 和 FMNH ⁻结合，K _d分别为17.4 ± 0.9 μm和4.08 ± 0.8 μm。_{在结合 DMSO 2}之前，需要将 FMN 与 DMSMO 结合。这也适用于还原的 FMN 与 DMSMO 的快速结合，然后是 DMSO ₂。用 FMNH ^-替代还原的 DMSR表现出相同的氧化动力学，表明 FMNH ^-从 DMSR 转移到了 DMSMO。^{FMNH -} :DMSMO的氧化，无论有无 DMSO _{2 ，}​​均不会产生任何用于单氧化的黄素加合物。因此，H ₂ O ₂很可能是攻击基材的反应剂。H ₂ O ₂测定结果表明， FMNH ^- :DMSMO的氧化产生了 H ₂ O ₂，​​而在 DMSO ₂存在的情况下没有检测到H ₂ O ₂，​​这证实了 H ₂ O ₂的利用。由快速骤冷流确定的甲亚磺酸盐形成的速率常数与黄素氧化的速率常数相似，表明H ₂ O _{2与DMSO 2}快速反应，以黄素氧化作为限速步骤。这是使用快速动力学研究两种组分的动力学机制以及使用 LC-MS 检测甲亚磺酸盐的方法的首次报告。