Abstract
The methyl-coenzyme M reductase (MCR) is a central enzyme in anaerobic microbial methane metabolism, which consists of methanogenesis and anaerobic oxidation of methane (AOM). MCR catalyzes the final step of methanogenesis and the first step of AOM to achieve the production and oxidation of methane, respectively. Besides a unique nickel tetrahydrocorphinoid (coenzyme F430), MCR also features several unusual post-translational modifications (PTMs), which are assumed to play important roles in regulating MCR functions. However, only few studies have been implemented on MCR PTMs. Therefore, to recapitulate current knowledge and prospect future studies, this review summarizes and discusses studies on MCR and its PTMs.
Highlights
Anaerobic microbial methane metabolism is one key part of the global carbon cycle, which controls the methane emission to the atmosphere (Kirschke et al, 2013; Evans et al, 2019)
Recent studies have changed our view of the MCR from its evolutionary perspective to its two remarkable features, the conenzyme F430 and unusual posttranslational modifications (PTMs) at the active site
A study has provided supportive evidence for the methyl radical mechanism (Wongnate et al, 2016), which was only based on methanogenesis, so more future studies are necessary to explore the reaction mechanism for coenzyme 430 during the anaerobic oxidation of methane (AOM)
Summary
Anaerobic microbial methane metabolism is one key part of the global carbon cycle, which controls the methane emission to the atmosphere (Kirschke et al, 2013; Evans et al, 2019). Methanogenic archaea and anaerobic methanotrophic archaea (ANME) in anoxic environments are the major groups involved in microbial methane metabolism (Enzmann et al, 2018). Methanogenic archaea use the end products of fermentation to produce methane anaerobically (Sieber et al, 2012; Vanwonterghem et al, 2016; Lyu et al, 2018b; Evans et al, 2019). MCRI and MCRII are the common isozymes of MCR found in methanogenic archaea They were firstly distinguished in Methanothermobacter marburgensis by anion exchange chromatography (Rospert et al, 1990). Based on phylogenetic reconstruction of MCRs, Wagner et al demonstrated a new type of MCR (highly structurally similar to MCRI and MCRII) exclusively from Methanococcales, so called MCRIII (Wagner et al, 2017). There is only one type of MCR found in ANME (Thauer, 2019)
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