Methanogenesis Biochemistry

Abstract

Methanogenesis is the biological production of methane mediated by anaerobic microorganisms from the Archaea domain commonly called methanogens. The production of methane is the energy‐yielding metabolism of methanogens and is unique to these organisms. Methane is produced by three major pathways: (1) reduction of carbon dioxide, (2) fermentation of acetate and (3) dismutation of methanol or methylamines. All three pathways have in common the demethylation of methyl– coenzyme M to methane and the reduction of the heterodisulfide of coenzyme M and coenzyme B catalysed by methyl–coenzyme M and heterodisulfide reductases . Investigations of the biochemistry of the pathways have revealed novel enzymes with metal and cofactor requirements that have introduced new principles of biochemistry. Key Concepts Methanogenesis is the final step in the biological decomposition of biomass in the absence of oxygen. Approximately 70% of biologically produced methane originates from conversion of the methyl group of acetate to methane. The pathway of methanogenesis involves enzymes with novel cofactor and metal requirements. Nickel is an essential metal that is found in the active site of carbon monoxide dehydrogenase, hydrogenase, and methyl–coenzyme M reductase, an enzyme which is common to all methanogenic pathways. Methyltransferases involved in the metabolism of methylamines by Methanosarcina species contain pyyrolysine, the 22nd amino acid. Comparative genomics combined with biochemical analyses have revealed variations in the enzymes involved in the energy‐conservation steps in methanogens. Energy conservation in methanogens is linked to the generation of a chemical gradient that drives ATP synthesis by an ATP synthase.

Effect of Silver Nanoparticles and Antibiotics on Antibiotic Resistance Genes in Anaerobic Digestion

“…Tetrahydromethanopterin (among other enzymes) catalyze the conversion of carbon dioxide to methane using hydrogen as an electron donor in hydrogenotrophic methanogens (Rouviere and Wolfe, 1988). Lessner (2009) reported H4MPT to be a structural analog to the enzyme tetrahydrosarcinapterin (H4SPT), which is involved in the shuttling of carbon from acetate's carboxyl group to methane by acetoclastic methanogens. Dimitru et al (2003) found that a competitive relationship between PABA and various PABA-like inhibitors for the active site on an enzyme (4-(b-d-ribofuranosyl)aminobenzene-5 0 -phosphate synthase) that catalyzes the first step in the biosynthesis of H4MPT.…”

Microbial drivers of methane emissions from unrestored industrial salt ponds

“…While they can be effective C sinks, wetlands are also the single largest natural source of atmospheric methane (~127−155 Tg annually) [5], a greenhouse gas with 25−35 times the global warming potential of CO 2 over a century timescale [6]. Methane production in wetlands is largely attributed to the activity of anaerobic archaeal methanogens [7]. Anaerobic archaea can produce methane via three pathways-by splitting acetate (acetoclastic methanogenesis), by reducing CO 2 using hydrogen as an electron donor (hydrogenotrophic methanogenesis), or by demethylating methyl-containing substrates such as methanol, methylamine, or dimethylsulfide (methylotrophic methanogenesis) [8].…”

Rumen Methanogenesis, Rumen Fermentation, and Microbial Community Response to Nitroethane, 2-Nitroethanol, and 2-Nitro-1-Propanol: An In Vitro Study

“…The hydrogenotrophic, methylotrophic, and acetoclastic pathways are the three major pathways for ruminal CH 4 production. The biochemical reactions and enzyme profiles involved in methanogenesis are well identified and described [37]. Methyl-coenzyme M reductase (mcr) is a key enzyme responsible for catalyzing the CH 4 -producing step in the process of methanogenesis.…”