Analysis of Substrate Specificity in CobT Homo logs Reveals Widespread Preference for DMB, the Lower Axial Ligand of Vitamin B12
Analysis of Substrate Specificity in CobT Homo logs Reveals Widespread Preference for DMB, the Lower Axial Ligand of Vitamin B12
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DOI：
10.1016/j.chembiol.2013.08.007
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发表时间：
2013-10-24
影响因子：
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通讯作者：
Taga, Michiko E.
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文献类型：
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作者：
Hazra, Amrita B.;Tran, Jennifer L. A.;Taga, Michiko E.
钴胺素如维生素B-12（钴胺素）仅由原核生物产生，并被许多其他生物用作各种代谢过程的辅助因子。钴化物是具有上下轴位配体的含钴四吡咯。在不同细菌产生的钴酰胺中，下配体的结构是不同的。我们通过探索CobT同源物的反应性来研究这种结构变异性的生化基础，CobT是一种负责激活下配体碱基并将其并入cobamides的酶。结果表明，CobT酶可以激活一系列下配体底物，并且大多数酶优先附着于钴胺素的下配体5,6-二甲基苯并咪唑（DMB）。这表明，许多在纯培养中合成钴胺素以外的钴胺素的细菌可能在混合群落中通过附着环境中可用的DMB产生钴胺素。
Cobamides such as vitamin B-12 (cobalamin) are produced exclusively by prokaryotes and used by many other organisms as cofactors for diverse metabolic processes. Cobamides are cobalt-containing tetrapyrroles with upper and lower axial ligands. The structure of the lower ligand varies in cobamides produced by different bacteria. We investigated the biochemical basis of this structural variability by exploring the reactivity of homologs of CobT, the enzyme responsible for activating lower ligand bases for incorporation into cobamides. Our results show that CobT enzymes can activate a range of lower ligand substrates, and the majority of the enzymes tested preferentially attach 5,6-dimethylbenzimidazole (DMB), the lower ligand of cobalamin. This suggests that many bacteria that synthesize cobamides other than cobalamin in pure culture may produce cobalamin in mixed communities by attaching DMB when it is available in the environment.