Methyl transfer in the methane-producing Archaea

     Methyl-corrinoids are essential to methane production in strictly anaerobic

methane-producing bacteria (Ferry 1993). Corrinoids serve to transfer methyl groups from methanogenic substrates to coenzyme M, a methanogen-specific enzyme. Different enzymes mediate methyl transfer from methanogenic substrates such as acetate (Ferry 1992), methylamines (Burke and Krzycki 1995), methanol (Keltjens and Vogels 1994), pyruvate (Bock et al. 1994), and methyltetrahydromethanopterin, an intermediate of methane-production from formate and CO2 (Poirot et al. 1987, Thauer et al. 1993). This last reaction is comparable to methionine synthesis in that the methyl group is transferred from an intermediate pterin to a thiol group via methyl-B12 (Poirot et al. 1987) Ribonucleotide reductases

     Ribonucleotide reductase catalyzes the conversion of ribonucleotides to the

deoxyribonucleotides required for DNA synthesis. Currently, four classes of reductase are known, each with their own different cofactor requirement and quaternary structure. The Ado-B12-dependent reductases belong to Class II and are usually found among microorganisms (Blakley and Barker 1964, Blakley 1965). Interestingly the reaction mechanism and active site of class II reductases appear very similar to the Class I reductase of E. coli (Booker et al. 1994), which uses means other than Ado-B12 to generate the free-radical required for catalysis (Reichard 1993). Degradation of recalcitrant compounds

      Corrinoids play an important role in the anaerobic degradation of 3-hydroxy ethers and hydroxy amines such as polyethylene glycol (Frings et al. 1992), and triethanolamine (Frings et al. 1994), which are generally thought to be recalcitrant to degradation in the absence of oxygen. In addition, past studies have suggested it is possible that the