Olson Kenneth R, Clear Kasey J, Takata Tsuyoshi, Gao Yan, Ma Zhilin, Pfaff Ella, Travlos Anthony, Luu Jennifer, Wilson Katherine, Joseph Zachary, Kyle Ian, Kasko Stephen M, Jones Prentiss, Fukuto Jon, Xian Ming, Wu Gang, Straub Karl D
Department of Physiology, Indiana University School of Medicine-South Bend Center, South Bend, IN 46617, USA.
Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
Antioxidants (Basel). 2024 May 20;13(5):619. doi: 10.3390/antiox13050619.
1,4-naphthoquinones (NQs) catalytically oxidize HS to per- and polysufides and sulfoxides, reduce oxygen to superoxide and hydrogen peroxide, and can form NQ-SH adducts through Michael addition. Here, we measured oxygen consumption and used sulfur-specific fluorophores, liquid chromatography tandem mass spectrometry (LC-MS/MS), and UV-Vis spectrometry to examine HS oxidation by NQs with various substituent groups. In general, the order of HS oxidization was DCNQ ~ juglone > 1,4-NQ > plumbagin >DMNQ ~ 2-MNQ > menadione, although this order varied somewhat depending on the experimental conditions. DMNQ does not form adducts with GSH or cysteine (Cys), yet it readily oxidizes HS to polysulfides and sulfoxides. This suggests that HS oxidation occurs at the carbonyl moiety and not at the quinoid 2 or 3 carbons, although the latter cannot be ruled out. We found little evidence from oxygen consumption studies or LC-MS/MS that NQs directly oxidize HS, and we propose that apparent reactions of NQs with inorganic polysulfides are due to HS impurities in the polysulfides or an equilibrium between HS and HS. Collectively, NQ oxidation of HS forms a variety of products that include hydropersulfides, hydropolysulfides, sulfenylpolysulfides, sulfite, and thiosulfate, and some of these reactions may proceed until an insoluble S colloid is formed.
1,4-萘醌（NQs）可催化将硫氢化物（HS）氧化为多硫化物和亚砜，将氧气还原为超氧化物和过氧化氢，并可通过迈克尔加成反应形成NQ-SH加合物。在此，我们测量了氧气消耗情况，并使用硫特异性荧光团、液相色谱串联质谱（LC-MS/MS）和紫外可见光谱法，来研究具有不同取代基的NQs对HS的氧化作用。总体而言，HS氧化的顺序为：二氯萘醌（DCNQ）胡桃醌>1,4-萘醌>白花丹素>二甲基萘醌（DMNQ）2-甲基萘醌>甲萘醌，不过这一顺序会因实验条件的不同而略有变化。DMNQ不会与谷胱甘肽（GSH）或半胱氨酸（Cys）形成加合物，但它能轻易地将HS氧化为多硫化物和亚砜。这表明HS的氧化发生在羰基部分，而非醌环的2或3位碳原子上，尽管不能排除后者的可能性。我们从氧气消耗研究或LC-MS/MS中几乎没有发现NQs直接氧化HS的证据，我们认为NQs与无机多硫化物的表观反应是由于多硫化物中的HS杂质，或者是HS与HS之间的平衡所致。总体而言，NQs对HS的氧化形成了多种产物，包括氢过硫化物、氢多硫化物、亚磺酰基多硫化物、亚硫酸盐和硫代硫酸盐，其中一些反应可能会持续进行，直到形成不溶性的硫胶体。
