生物谷报道：维生素B12（钴胺素）是已知最大的非聚合物天然产物之一，是惟一完全由微生物合成的一种维生素。尽管进行了多年研究，但科学家对该维生素的一部分的生物合成仍然很不了解。现在，研究人员终于揭示了其生物合成中的最后一个未知步骤。该研究成果发表在最新一期的《Nature》杂志上。
研究发现一种被命名为BluB的物质在维生素B12的生物合成中发挥作用。BluB的X-射线晶体结构已被确定。它是一种酶，利用分子氧来分解黄素（四羟酮醇）单核苷酸共因子，形成维生素B12的低配体。这一反应是一例不寻常的过程，即一种共因子在酶催化下被破坏来合成另一种共因子。
FIGURE 1. BluB catalyses DMB production.
a, Overall scheme for DMB biosynthesis and B12 formation. The atoms converted to DMB are shown in red; the reaction catalysed by BluB is in the red box. b, HPLC traces (280 nm) of reactions containing 10 M BluB, 20 mM NADH and 100 M FMN, or lacking the indicated components. Similar conversion was observed in reactions containing NADPH instead of NADH (not shown). In the absence of NAD(P)H, trace amounts of product formed, probably through adventitious photoreduction of FMN followed by turnover in the active site. c, Calcofluor fluorescence of the bluB mutant. d, Growth of wild-type S. meliloti and the bluB mutant. e, Radio-TLC of the BluB reaction containing [32P]FMN. Arrows represent migration of standards. The same result was obtained using two additional eluant systems (data not shown).
原文出处：
Nature Volume 446 Number 7134
BluB cannibalizes flavin to form the lower ligand of vitamin B12 p449
Michiko E. Taga, Nicholas A. Larsen, Annaleise R. Howard-Jones, Christopher T. Walsh and Graham C. Walker
doi:10.1038/nature05611
First paragraph | Full Text | PDF (2,045K) | Supplementary information
See also: Editor's summary | News and Views by Ealick & Begley
作者简介：
Graham C. Walker, Ph.D.
Dr. Walker is a professor in the Department of Biology at the Massachusetts Institute of Technology (MIT) and a director of MIT's Introductory Biology Program. He received his B.Sc. degree from Carleton University and his Ph.D. from the University of Illinois at Urbana-Champaign. In addition, he was a postdoctoral fellow at both the University of Illinois at Urbana-Champaign and the University of California–Berkeley.
Dr. Walker was recently named an American Cancer Society Research Professor. He has received several awards, including the Charles Ross Scholar Award for Cancer Research, the Arthur C. Smith Award (for contributions to undergraduate life), and the 2006 Environmental Mutagen Society Award. He has served as an editor of the Journal of Bacteriology for 16 years, finishing a 10-year term as editor-in-chief in 2001. He has also been a Sigma Xi Distinguished Visiting Professor (New Jersey Medical School) and participated in the Stone Lectureship, Pennsylvania State University. In addition, he is a fellow of the American Academy of Microbiology (1994) and serves on the editorial boards of DNA Repair, Mutation Research, and Current Opinion in Microbiology as well as on the editorial committee of the Annual Review of Microbiology.
RESEARCH ABSTRACT SUMMARY:
Graham Walker studies how cells respond to DNA damage as well as the biological interdependence of certain bacteria and plants. He will establish an education group—composed of postdoctoral fellows, graduate students, and undergraduates—to focus on curricular development, including Web-based materials, for introductory biology.
View Research Abstract
