Radical mechanisms in adenosylmethionine- and adenosylcobalamin-dependent enzymatic reactions.
A class of enzymatic reactions of S-adenosylmethionine (AdoMet) has recently been recognized, in which AdoMet plays a novel role by initiating free radical formation through the intermediate formation of 5'-deoxyadenosine-5'-yl, the 5'-deoxyadenosyl radical. The reactions are in this way related to adenosylcobalamin-dependent processes, which also depend on the formation of the 5'-deoxyadenosyl radical as an intermediate. The mechanisms by which the 5'-deoxyadenosyl radical is generated by the AdoMet- and adenosylcobalamin-dependent enzymes are very different. However, the functions of the 5'-deoxyadenosyl radical are similar in that in all cases it abstracts hydrogen from a substrate to form 5'-deoxyadenosine and a substrate-derived free radical. In this paper, the role of the 5'-deoxyadenosyl radical in the reaction of the adenosylcobalamin-dependent reactions will be compared with its role in the AdoMet-dependent reaction of lysine 2,3-aminomutase. The mechanism by which AdoMet is cleaved to the 5'-deoxyadenosyl radical at enzymatic sites will also be discussed.
Frey
P A
PA
Department of Biochemistry, University of Wisconsin-Madison 53705, USA. frey@biochem.wisc.edu
Reed
G H
GH
D001665:Binding Sites; D003038:Cobamides / Q000737:chemistry* / Q000378:metabolism*; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism*; D005609:Free Radicals; D019751:Intramolecular Transferases / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D011408:Propanediol Dehydratase / Q000737:chemistry / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry* / Q000378:metabolism*
D003038:Cobamides; D004798:Enzymes; D005609:Free Radicals; D012436:S-Adenosylmethionine; D011408:Propanediol Dehydratase; D019751:Intramolecular Transferases; C021518:lysine 2,3-aminomutase; C000913:cobamamide