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キーワード:
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要旨:
Methane is a potent greenhouse gas that is generated and consumed in anaerobic environments through the energy metabolism of methanogens and anaerobic methanotrophic archaea (ANME), respectively. Coenzyme F-430 is essential for methanogenesis, and a structural variant of F-430, 17(2)-methylthio-F-430 (F-430-2), is found in ANME and is presumably essential for the anaerobic oxidation of methane. Here we use liquid chromatography-high-resolution mass spectrometry to identify several new structural variants of F-430 in the cell extracts of selected methanogens and ANME. Methanocaldococcus jannaschii and Methanococcus maripaludis contain an F-430 variant (denoted F-430-3) that has an M+ of 1,009.2781. This mass increase of 103.9913 over that of F-430 corresponds to C3H4O2S and is consistent with the addition of a 3-mercaptopropionate moiety bound as a thioether followed by a cyclization. The UV absorbance spectrum of F-430-3 was different from that of F-430 and instead matched that of an F-430 derivative where the 17(3) keto moiety had been reduced. This is the first report of a modified F-430 in methanogens. In a search for F-430-2 and F-430-3 in other methanogens and ANME, we have identified a total of nine modified F-430 structures. One of these compounds may be an abiotic oxidative product of F-430, but the others represent naturally modified versions of F-430. This work indicates that F-430-related molecules have additional functions in nature and will inspire further research to determine the biochemical role(s) of these variants and the pathways involved in their biosynthesis.
