RECENT ADVANCES IN ELUCIDATION OF BIOLOGICAL CORRINOID FUNCTIONS

Eleven adenosylcorrinoid-dependent rearrangements and elimination reac tions have been described during the last four decades of vitamin B-12 research. In contrast, only the cobamide-dependent methionine synthas e was well established as a corrinoid-dependent methyl transfer reacti on. Yet, investigations during the last few years revealed nine additi onal corrinoid-dependent methyltransferases. Many of these reactions a re catalyzed by bacteria which possess a distinct C1 metabolism. Notab ly acetogenic and methanogenic bacteria carry out such methyl transfer s in their anabolism and catabolism. Tetrahydrofolate or a similar pte rine derivative is a key intermediate in these reactions. It functions as methyl acceptor and the methylated tetrahydrofolate serves as a me thyl donor.