School of Bioscience and Biotechnology , Tokyo University of Technology , 1404-1 Katakura-cho , Hachioji , Tokyo 192-0982 , Japan.
J Org Chem. 2019 Mar 15;84(6):3552-3558. doi: 10.1021/acs.joc.9b00163. Epub 2019 Mar 4.
Previously, we identified that parabanic acid (PA) and its hydrolysate, oxaluric acid (OUA), are the singlet oxygen-specific oxidation products of uric acid (UA). In this study, we investigated the PA formation mechanism by using HPLC and a time-of-flight mass spectrometry technique and identified unknown intermediates as (2,5-dioxoimidazolidin-4-ylidene)aminocarbonylcarbamic acid (DIAA), dehydroallantoin, and 4-hydroxyallantoin (4-HAL). DIAA is the key to PA production, and its formation pathway was characterized using O and HO. Two oxygen atoms were confirmed to be incorporated into DIAA: the 5-oxo- oxygen from singlet oxygen and the carboxylic oxygen from water. Isolated DIAA and 4-HAL gave PA stoichiometrically. A plausible reaction scheme in which two pathways branch out from DIAA is presented, and the potential for PA as an endogenous probe for biological formation of singlet oxygen is discussed.
先前，我们鉴定出胍基乙酸（PA）及其水解产物，尿囊素酸（OUA），是尿酸（UA）产生的单线态氧特异性氧化产物。在这项研究中，我们使用 HPLC 和飞行时间质谱技术来研究 PA 的形成机制，并鉴定出未知的中间体为（2,5-二氧代咪唑烷-4-亚基）氨基甲酰氨基甲酸（DIAA）、去氢尿囊素和 4-羟基尿囊素（4-HAL）。DIAA 是 PA 产生的关键，其形成途径采用 O 和 HO 进行了表征。有两个氧原子被证实被整合到 DIAA 中：单线态氧的 5-氧和水的羧酸氧。分离出的 DIAA 和 4-HAL 可与 PA 进行化学计量反应。提出了一个可能的反应方案，其中两条途径从 DIAA 分支出来，并讨论了 PA 作为生物生成单线态氧的内源性探针的潜力。
