Vitamin B-12 is one of eight B vitamins which is important for the normal functioning of the brain and nervous system, and for the formation of blood. It is normally involved in the metabolism of every cell of the body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production.

It is one of the most alluring and fascinating molecules in the world of science and medicine.

B12的结构十分复杂。它的结构的阐明和合成途径是由Robert Burns Woodward and Albert Eschenmoser两位科学家带领100多名学生和博士后研究花了数年时间才得以完成。他们的工作因此也获得了1965年的诺贝尔化学奖。

动物和植物都不能自身合成维生素B12,只有细菌具有合成维生素B12的能力。能合成维生素的细菌有：Aerobacter, Agrobacterium, Alcaligenes, Azotobacter, Bacillus, Clostridium, Corynebacterium, Flavobacterium, Micromonospora, Mycobacterium, Nocardia, Propionibacterium, Protaminobacter, Proteus, Pseudomonas, Rhizobium, Salmonella, Serratia, Streptomyces, Streptococcus and Xanthomonas. 需要注意的是，E. coli不能合成维生素B12.

工业上生产B12即是通过微生物发酵的方式进行的。目前用得最多是脱氮假单胞菌(Pseudomonas denitrificans )和Propionibacterium shermanii.

这里推荐两篇文献：

1、Microbial production of vitamin B12

摘要：One of the most alluring and fascinating molecules in the world of science and medicine is vitamin B12 (cobalamin), which was originally discovered as the anti pernicious anemia factor and whose enigmatic complex structure is matched only by the beguiling chemistry that it mediates. The biosynthesis of this essential nutrient is intricate, involved and, remarkably, confined to certain members of the prokaryotic world, seemingly never have to have made the eukaryotic transition. In humans, the vitamin is required in trace amounts (approximately 1 µg/day) to assist the actions of only two enzymes, methionine synthase and (R)-methylmalonyl-CoA mutase; yet commercially more than 10 t of B12 are produced each year from a number of bacterial species. The rich scientific history of vitamin B12 research, its biological functions and the pathways employed by bacteria for its de novo synthesis are described. Current strategies for the improvement of vitamin B12 production using modern biotechnological techniques are outlined.

2、Woodward’s Synthesis of Vitamin B12

摘要：The synthesis of this molecule was a landmark in organic synthesis. It involved the masterful control of shapes of molecules to create 9 chiral centres with known absolute and relative configurations. The concepts of absolute and induced asymmetric synthesis are here explained.

 

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