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Model Studies for the B12 Dependent Methyltransferases

  • Tamis Darbre

Abstract

Methytransferases having coenzyme B12 and other Co-eorrinoids as cofactors, catalyze important methyl transfer reactions (1,2). The synthesis of methionine, in most animals including mammals and many bacteria, involves the transfer of the methyl group from Me-tetrahydrofolate to Cob(I)alamin and subsequently to homocysteine (3). In acetogenic bacteria, the transfer from Me-tetrahydrofolate to Co(I) is followed by further reaction with CO and RSH in a Co-Ni dependent enzyme (4). In methanogenic bacteria, corrinoids are involved in the synthesis of coenzyme M and can use methanol and Me-tetrahydrofolate as methyl sources. Methanol is also the methyl donor in other acetogenic bacteria (5). The enzymatic reaction catalyzed by methionine synthase is shown in Scheme 1; in the first half-reaction, Co(I) acts as a supernucleophile for the substrate bearing the CH3-group, Me-THF, whereas it becomes an efficient leaving group in the second half-reaction. In the latter step, the methyl cob(III)alamin reacts with homocysteine to form methionine and regenerate the Cob(I)alamin (6).

Keywords

Tertiary Amine Dimethyl Aniline Methyl Transfer Acetogenic Bacterium Methanosarcina Barkeri 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2002

Authors and Affiliations

  • Tamis Darbre
    • 1
  1. 1.Department of Chemistry and BiochemistryUniversity of BernBernSwitzerland

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