Hydrogen Sulfide Oxidation by Myoglobin

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• 作者：Trever Bostelaar ; Victor Vitvitsky ; Jacques Kumutima ; Brianne E. Lewis ; Pramod K. Yadav ; Thomas C. Brunold ; Milos Filipovic ; Nicolai Lehnert ; Timothy L. Stemmler ; Ruma Banerjee
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：July 13, 2016
• 年：2016
• 卷：138
• 期：27
• 页码：8476-8488
• 全文大小：761K
• 年卷期：0
• ISSN：1520-5126

文摘

Enzymes in the sulfur network generate the signaling molecule, hydrogen sulfide (H₂S), from the amino acids cysteine and homocysteine. Since it is toxic at elevated concentrations, cells are equipped to clear H₂S. A canonical sulfide oxidation pathway operates in mitochondria, converting H₂S to thiosulfate and sulfate. We have recently discovered the ability of ferric hemoglobin to oxidize sulfide to thiosulfate and iron-bound hydropolysulfides. In this study, we report that myoglobin exhibits a similar capacity for sulfide oxidation. We have trapped and characterized iron-bound sulfur intermediates using cryo-mass spectrometry and X-ray absorption spectroscopy. Further support for the postulated intermediates in the chemically challenging conversion of H₂S to thiosulfate and iron-bound catenated sulfur products is provided by EPR and resonance Raman spectroscopy in addition to density functional theory computational results. We speculate that the unusual sensitivity of skeletal muscle cytochrome c oxidase to sulfide poisoning in ethylmalonic encephalopathy, resulting from the deficiency in a mitochondrial sulfide oxidation enzyme, might be due to the concentration of H₂S by myoglobin in this tissue.