Methane metabolism

Methane is metabolized principally by methanotrophs and the methanogens in the global carbon cycle. Methanotrophs consume methane as the only source of carbon, while methanogens produce methane as a metabolic byproduct. Methylotrophs, which are microorganisms that can obtain energy for growth by oxidizing one-carbon compounds, such as methanol and methane, are situated between methanotrophs and methanogens. In this map, formaldehyde is placed at the diverging point for further oxidation to CO2 for energy source and assimilation for biosynthesis in methanotrophs and methyltrophs. There are three pathways that convert formaldehyde to C2 or C3 compounds: serine pathway [MD:M00346], ribulose monophosphate pathway [MD:M00345], and xylulose monophosphate pathway [MD:M00344]. The first two pathways are found in prokaryotes and the third is found in yeast. As a special case of methylotrophs, various amines can be used as carbon sources in trimethylamine metabolism. In contrast, methanogens can obtain energy for growth by converting a limited number of substrates to methane under anaerobic conditions. Only three types of methanogenic pathways are known: methanogenesis from H2/CO2 or formate [MD:M00347], methanol to methane [MD:M00356], and acetate to methane [MD:M00357]. Methanogens use 2-mercaptoethanesulfonate (CoM; coenzyme M) as the terminal methyl carrier in methanogenesis and have four enzymes for CoM biosynthesis [MD:M00358]. Coenzyme B-Coenzyme M heterodisulfide reductase (Hdr), requiring for the final reaction steps of methanogenic pathway, is divided into two types: cytoplasmic HdrABC in most methanogens and membrane-bound HdrED in Methanosarcina species.

Metabolism; Energy metabolism

PMID:11830598

Graham DE, Xu H, White RH

Identification of coenzyme M biosynthetic phosphosulfolactate synthase: a new family of sulfonate-biosynthesizing enzymes.

J Biol Chem 277:13421-9 (2002)

PMID:15168610

Deppenmeier U

The membrane-bound electron transport system of Methanosarcina species.

J Bioenerg Biomembr 36:55-64 (2004)

PMID:15353801

Hallam SJ, Putnam N, Preston CM, Detter JC, Rokhsar D, Richardson PM, DeLong EF

Reverse methanogenesis: testing the hypothesis with environmental genomics.

Science 305:1457-62 (2004)

PMID:16024727

Welander PV, Metcalf WW

Loss of the mtr operon in Methanosarcina blocks growth on methanol, but not methanogenesis, and reveals an unknown methanogenic pathway.

Proc Natl Acad Sci U S A 102:10664-9 (2005)

PMID:16278835

Yurimoto H, Kato N, Sakai Y

Assimilation, dissimilation, and detoxification of formaldehyde, a central metabolic intermediate of methylotrophic metabolism.

Chem Rec 5:367-75 (2005)

PMID:16385054

Fricke WF, Seedorf H, Henne A, Kruer M, Liesegang H, Hedderich R, Gottschalk G, Thauer RK.

The genome sequence of Methanosphaera stadtmanae reveals why this human intestinal archaeon is restricted to methanol and H2 for methane formation and ATP synthesis.

J Bacteriol 188:642-58 (2006)

PMID:16428816

Kato N, Yurimoto H, Thauer RK

The physiological role of the ribulose monophosphate pathway in bacteria and archaea.

Biosci Biotechnol Biochem 70:10-21 (2006)

PMID:18587410

Thauer RK, Kaster AK, Seedorf H, Buckel W, Hedderich R

Methanogenic archaea: ecologically relevant differences in energy conservation.

Nat Rev Microbiol 6:579-91 (2008)

PMID:20437165

Liffourrena AS, Salvano MA, Lucchesi GI

Pseudomonas putida A ATCC 12633 oxidizes trimethylamine aerobically via two different pathways.

Arch Microbiol 192:471-6 (2010)