mesna and methanopterin

Methanogenesis, the anaerobic production of methane from CO2 or simple carbon compounds, requires seven organic coenzymes. This review describes pathways for the biosynthesis of methanofuran, 5,6,7,8-tetrahydromethanopterin, coenzyme F420, coenzyme M (2-mercaptoethanesulfonic acid) and coenzyme B (7-mercaptoheptanoyl-L-threonine phosphate). Spectroscopic evidence for the pathways is reviewed and recent efforts are described to identify and characterize the biosynthetic enzymes from methanogenic archaea. The literature from 1971 to September 2001 is reviewed, and 169 references are cited.

Topics: Archaea; Carbon Dioxide; Coenzymes; Diterpenes; Euryarchaeota; Furans; Genomics; Magnetic Resonance Spectroscopy; Mesna; Methane; Molecular Structure; Phosphothreonine; Pterins; Riboflavin

Our current knowledge of the pathways and genes involved in the biosynthesis of the methanogenic coenzymes methanopterin, coenzyme B, methanofuran, coenzyme F420, and coenzyme M is presented. Proposed reaction mechanisms for several of the novel reactions involved in the pathways are presented.

Topics: Coenzymes; Furans; Gene Expression Regulation, Archaeal; Mesna; Methanococcus; Molecular Structure; Phosphothreonine; Pterins; Riboflavin

Topics: Cobamides; Coenzymes; Euryarchaeota; Furans; Mesna; Metalloporphyrins; Metalloproteins; Methane; Molecular Structure; Nickel; Phosphothreonine; Pterins; Riboflavin

Formaldehyde oxidation by cell-free extracts of Methanobacterium thermoautotrophicum was shown to drive methanogenesis from CH3-S-coenzyme M or HCHO under a nonreductive atmosphere of N2. Under N2 when HCHO was the sole source of carbon and reducing equivalents in the reaction, it underwent oxidation and reduction events (disproportionation), the sum of the reactions being 3 HCHO + H2O----CH4 + 2 HCOO - + 2H+. This reaction predicts a CH4/HCHO ratio of 1/3, which is in agreement with the experimental finding of 1/2.9. In extracts of the mesophilic methanogen Methanococcus voltae and the extreme thermophile Methanococcus jannaschii , which exhibited formate dehydrogenase activity, the CH4/HCHO ratio was 1/2. NADPH stimulated methane formation from HCHO under N2. An unidentified, oxygen-labile cofactor, the formaldehyde activation factor, present in boiled-cell extract was discovered. Methanopterin , an oxygen-stable molecule, also substituted for boiled-cell extract.

Topics: Euryarchaeota; Formaldehyde; Mesna; Methane; NADP; Oxidation-Reduction; Pterins