Bridwell-Rabb Jennifer, Drennan Catherine L
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Curr Opin Chem Biol. 2017 Apr;37:63-70. doi: 10.1016/j.cbpa.2017.01.013. Epub 2017 Feb 3.
The ability of cobalamin to coordinate different upper axial ligands gives rise to a diversity of reactivity. Traditionally, adenosylcobalamin is associated with radical-based rearrangements, and methylcobalamin with methyl cation transfers. Recently, however, a new role for adenosylcobalamin has been discovered as a light sensor, and a methylcobalamin-dependent enzyme has been identified that is suggested to transfer a methyl anion. Additionally, recent studies have provided a wealth of new information about a third class of cobalamin-dependent enzymes that do not appear to use an upper ligand. They function in reductive dehalogenations and epoxide reduction reactions. Finally, mechanistic details are beginning to emerge about the cobalamin-dependent S-adenosylmethionine radical enzyme superfamily for which the role of cobalamin has been largely enigmatic.
钴胺素与不同的上轴向配体配位的能力导致了反应多样性。传统上，腺苷钴胺素与基于自由基的重排有关，而甲基钴胺素与甲基阳离子转移有关。然而，最近发现了腺苷钴胺素作为光传感器的新作用，并且鉴定出一种依赖甲基钴胺素的酶，该酶被认为可转移甲基阴离子。此外，最近的研究提供了大量关于第三类不使用上配体的钴胺素依赖性酶的新信息。它们在还原性脱卤和环氧化物还原反应中起作用。最后，关于钴胺素依赖性S-腺苷甲硫氨酸自由基酶超家族的机制细节开始浮现，而钴胺素在其中的作用在很大程度上一直是个谜。
