Pseudoperoxidase investigations of hydroperoxides and inhibitors with human lipoxygenases

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• 作者：Eric K. Hoobler ; Charles Holz ; Theodore R. Holman ; ^{tholman@chemistry.ucsc.edu}
• 关键词：LOX ; lipoxygenase ; 15-LOX-2 ; human epithelial 15-lipoxygenase-2 ; 15-LOX-1 ; human reticulocyte 15-lipoxygenase-1 ; 12-LOX ; human platelet 12-lipoxygenase ; soybean LOX-1 ; soybean lipoxygenase-1 ; 5-LOX ; human 5-lipoxygenase ; COX ; cyclooxygenase ; AA ; arachidon
• 刊名：Bioorganic and Medicinal Chemistry
• 出版年：2013
• 出版时间：1 July, 2013
• 年：2013
• 卷：21
• 期：13
• 页码：3894-3899
• 全文大小：437 K

文摘

Understanding the mode of action for lipoxygenase (LOX) inhibitors is critical to determining their efficacy in the cell. The pseudoperoxidase assay is an important tool for establishing if a LOX inhibitor is reductive in nature, however, there have been difficulties identifying the proper conditions for each of the many human LOX isozymes. In the current paper, both the 234 nM decomposition (UV) and iron-xylenol orange (XO) assays are shown to be effective methods of detecting pseudoperoxidase activity for 5-LOX, 12-LOX, 15-LOX-1 and 15-LOX-2, but only if 13-(S)-HPODE is used as the hydroperoxide substrate. The AA products, 12-(S)-HPETE and 15-(S)-HPETE, are not consistent hydroperoxide substrates since they undergo a competing transformation to the di-HETE products. Utilizing the above conditions, the selective 12-LOX and 15-LOX-1 inhibitors, probes for diabetes, stroke and asthma, are characterized for their inhibitory nature. Interestingly, ascorbic acid also supports the pseudoperoxidase assay, suggesting that it may have a role in maintaining the inactive ferrous form of LOX in the cell. In addition, it is observed that nordihydroguaiaretic acid (NDGA), a known reductive LOX inhibitor, appears to generate radical species during the pseudoperoxidase assay, which are potent inhibitors against the human LOX isozymes, producing a negative pseudoperoxidase result. Therefore, inhibitors that do not support the pseudoperoxidase assay with the human LOX isozymes, should also be investigated for rapid inactivation, to clarify the negative pseudoperoxidase result.