Raux E, Schubert H L, Warren M J
School of Biological Sciences, Queen Mary and Westfield College, London, UK.
Cell Mol Life Sci. 2000 Dec;57(13-14):1880-93. doi: 10.1007/PL00000670.
The biosynthesis of cobalamin (vitamin B12) is described, revealing how the concerted action of around 30 enzyme-mediated steps results in the synthesis of one of Nature's most structurally complex 'small molecules'. The plethora of genome sequences has meant that bacteria capable of cobalamin synthesis can be easily identified and their biosynthetic genes compared. Whereas only a few years ago cobalamin synthesis was thought to occur by one of two routes, there are apparently a number of variations on these two pathways, where the major differences seem to be concerned with the process of ring contraction. A comparison of what is currently known about these pathways is presented. Finally, the process of cobalt chelation is discussed and the structure/function of the cobalt chelatase associated with the oxygen-independent pathway (CbiK) is described.
本文描述了钴胺素（维生素B12）的生物合成过程，揭示了约30个酶介导步骤的协同作用是如何导致自然界中结构最复杂的“小分子”之一的合成。大量的基因组序列意味着能够合成钴胺素的细菌很容易被识别，并且可以对它们的生物合成基因进行比较。就在几年前，人们还认为钴胺素的合成是通过两条途径之一进行的，而现在这两条途径显然存在许多变体，主要差异似乎与环收缩过程有关。本文对目前已知的这些途径进行了比较。最后，讨论了钴螯合过程，并描述了与不依赖氧气途径相关的钴螯合酶（CbiK）的结构/功能。
