Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are common in wetlands, where they are responsible for marsh gas, and can occur in the digestive tracts of animals including ruminants and humans, where they are responsible for the methane content of belching and flatulence. In marine sediments, the biological production of methane, termed methanogenesis, is generally confined to where sulfates are depleted below the top layers. Methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Other methanogens are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of Earth's crust, kilometers below the surface.
A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2), as shown below:
In enzymology, a hydroxymethylglutaryl-CoA reductase (NADPH) (EC 1.1.1.34) is an enzyme that catalyzes the chemical reaction
In enzymology, a cytochrome-c3 hydrogenase (EC 1.12.2.1) is an enzyme that catalyzes the chemical reaction
In enzymology, ferredoxin hydrogenase, also referred to as [Fe-Fe]hydrogenase, H2 oxidizing hydrogenase, H2 producing hydrogenase, bidirectional hydrogenase, hydrogenase (ferredoxin), hydrogenlyase, and uptake hydrogenase, is found in Clostridium pasteurianum, Clostridium acetobutylicum,Chlamydomonas reinhardtii, and other organisms. The systematic name of this enzyme is hydrogen:ferredoxin oxidoreductase
In enzymology, a hydrogenase (acceptor) (EC 1.12.99.6) is an enzyme that catalyzes the chemical reaction
In enzymology, a hydrogen dehydrogenase (EC 1.12.1.2) is an enzyme that catalyzes the chemical reaction
In enzymology, a hydrogen:quinone oxidoreductase (EC 1.12.5.1) is an enzyme that catalyzes the chemical reaction
In enzymology, a Methanosarcina-phenazine hydrogenase (EC 1.12.98.3) is an enzyme that catalyzes the chemical reaction
In enzymology, a 5,10-methylenetetrahydromethanopterin reductase (EC 1.5.98.2) is an enzyme that catalyzes the chemical reaction
In enzymology, a CoB—CoM heterodisulfide reductase (EC 1.8.98.1) is an enzyme that catalyzes the chemical reaction
In enzymology, a methylenetetrahydromethanopterin dehydrogenase (EC 1.5.98.1) is an enzyme that catalyzes the chemical reaction
Coenzyme F420 or 8-hydroxy-5-deazaflavin is a coenzyme (sometimes called a cofactor) involved in redox reactions in methanogens, in many Actinomycetota, and sporadically in other bacterial lineages. It is a flavin derivative with an absorption maximum at 420 nm—hence its name. The coenzyme is a substrate for coenzyme F420 hydrogenase, 5,10-methylenetetrahydromethanopterin reductase and methylenetetrahydromethanopterin dehydrogenase.
Methanocaldococcus jannaschii is a thermophilic methanogenic archaean in the class Methanococci. It was the first archaeon, and third organism, to have its complete genome sequenced. The sequencing identified many genes unique to the archaea. Many of the synthesis pathways for methanogenic cofactors were worked out biochemically in this organism, as were several other archaeal-specific metabolic pathways.
Glucose-6-phosphate dehydrogenase (coenzyme-F420) is an enzyme with systematic name D-glucose-6-phosphate:F420 1-oxidoreductase. This enzyme catalyses the following chemical reaction
Formate dehydrogenase (acceptor) (EC 1.1.99.33, FDHH, FDH-H, FDH-O, formate dehydrogenase H, formate dehydrogenase O) is an enzyme with systematic name formate:acceptor oxidoreductase. This enzyme catalyses the following chemical reaction
8-Hydroxy-5-deazaflavin:NADPH oxidoreductase (EC 1.5.1.40, 8-OH-5dFl:NADPH oxidoreductase) is an enzyme with systematic name reduced coenzyme F420:NADP+ oxidoreductase. This enzyme catalyses the following chemical reaction
NADH:ubiquinone reductase (non-electrogenic) (EC 1.6.5.9, NDH-2, ubiquinone reductase, coenzyme Q reductase, dihydronicotinamide adenine dinucleotide-coenzyme Q reductase, DPNH-coenzyme Q reductase, DPNH-ubiquinone reductase, NADH-coenzyme Q oxidoreductase, NADH-coenzyme Q reductase, NADH-CoQ oxidoreductase, NADH-CoQ reductase) is an enzyme with systematic name NADH:ubiquinone oxidoreductase. This enzyme catalyses the following chemical reaction:
Hydrogenase (NAD+, ferredoxin) (EC 1.12.1.4, bifurcating [FeFe] hydrogenase) is an enzyme with systematic name hydrogen:NAD+, ferredoxin oxidoreductase. This enzyme catalyses the following chemical reaction
2-phospho-L-lactate transferase is an enzyme with systematic name (2S)-lactyl-2-diphospho-5'-guanosine:7,8-didemethyl-8-hydroxy-5-deazariboflavin 2-phospho-L-lactate transferase. This enzyme catalyses the following chemical reaction
