Matthews Rowena G, Koutmos Markos, Datta Supratim
Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA.
Curr Opin Struct Biol. 2008 Dec;18(6):658-66. doi: 10.1016/j.sbi.2008.11.005.
Methyltransferases that employ cobalamin cofactors, or their analogs the cobamides, as intermediates in catalysis of methyl transfer play vital roles in energy generation in anaerobic unicellular organisms. In a broader range of organisms they are involved in the conversion of homocysteine to methionine. Although the individual methyl transfer reactions catalyzed are simple S(N)2 displacements, the required change in coordination at the cobalt of the cobalamin or cobamide cofactors and the lability of the reduced Co(+1) intermediates introduces the necessity for complex conformational changes during the catalytic cycle. Recent spectroscopic and structural studies on several of these methyltransferases have helped to reveal the strategies by which these conformational changes are facilitated and controlled.
利用钴胺素辅因子或其类似物钴胺酰胺作为甲基转移催化中间体的甲基转移酶，在厌氧单细胞生物的能量产生中起着至关重要的作用。在更广泛的生物体中，它们参与同型半胱氨酸向甲硫氨酸的转化。尽管所催化的各个甲基转移反应都是简单的双分子亲核取代（S(N)2）反应，但钴胺素或钴胺酰胺辅因子钴原子上所需的配位变化以及还原态Co(+1)中间体的不稳定性，使得在催化循环中必须进行复杂的构象变化。最近对其中几种甲基转移酶的光谱和结构研究，有助于揭示促进和控制这些构象变化的策略。
