Frey P A, Reed G H
Department of Biochemistry, University of Wisconsin-Madison 53705, USA.
Arch Biochem Biophys. 2000 Oct 1;382(1):6-14. doi: 10.1006/abbi.2000.2010.
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.
最近人们认识到了一类S-腺苷甲硫氨酸（AdoMet）的酶促反应，其中AdoMet通过中间体5'-脱氧腺苷-5'-基（即5'-脱氧腺苷自由基）的形成引发自由基生成，从而发挥着新的作用。这些反应因此与依赖腺苷钴胺素的过程相关，后者也依赖于5'-脱氧腺苷自由基作为中间体的形成。由依赖AdoMet和依赖腺苷钴胺素的酶生成5'-脱氧腺苷自由基的机制非常不同。然而，5'-脱氧腺苷自由基的功能是相似的，即在所有情况下它都从底物中提取氢以形成5'-脱氧腺苷和底物衍生的自由基。在本文中，将比较5'-脱氧腺苷自由基在依赖腺苷钴胺素反应中的作用与其在赖氨酸2,3-氨基变位酶的依赖AdoMet反应中的作用。还将讨论AdoMet在酶促位点裂解为5'-脱氧腺苷自由基的机制。
