Characterization of the enzyme CbiH60 involved in anaerobic ring contraction of the cobalamin (vitamin B12) biosynthetic pathway.
Characterization of the enzyme CbiH60 involved in anaerobic ring contraction of the cobalamin (vitamin B12) biosynthetic pathway.
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参与钴胺素（维生素 B12）生物合成途径无氧环收缩的酶 CbiH60 的表征。
DOI：
10.1074/jbc.m112.422535
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Moore SJ
中科院分区：
文献类型：
--
作者：
Moore SJ
钴胺素（维生素B12）的生物合成的厌氧途径仍然很差，因为该途径中间体对氧的敏感性和酶的低活性。厌氧途径中的主要瓶颈之一是环收缩步骤，这在以前用纯化的酶系统没有观察到。革兰氏阳性需氧菌巨大芽孢杆菌具有完整的厌氧途径，该途径包含一种不寻常的环收缩酶CbiH 60，该酶具有与亚硝酸盐/亚硫酸盐还原酶家族序列相似的C末端延伸。为了提高溶解度，在宿主B中同源地产生酶。megateriumDSM 319. CbiH 60的电子顺磁共振表征表明，含有一个[4Fe-4S]中心。使用纯化的重组CbiH 60进行的分析表明，该酶可将钴前体蛋白-3和钴因子III高产率转化为环收缩产物钴前体蛋白-4，后者的转化取决于DTT和完整的Fe-S中心。此外，环收缩过程中，不涉及大环的中心钴离子的氧化态的变化。
The anaerobic pathway for the biosynthesis of cobalamin (vitamin B12) has remained poorly characterized because of the sensitivity of the pathway intermediates to oxygen and the low activity of enzymes. One of the major bottlenecks in the anaerobic pathway is the ring contraction step, which has not been observed previously with a purified enzyme system. The Gram-positive aerobic bacteriumBacillus megateriumhas a complete anaerobic pathway that contains an unusual ring contraction enzyme, CbiH60, that harbors a C-terminal extension with sequence similarity to the nitrite/sulfite reductase family. To improve solubility, the enzyme was homologously produced in the hostB. megateriumDSM319. CbiH60was characterized by electron paramagnetic resonance and shown to contain a [4Fe-4S] center. Assays with purified recombinant CbiH60demonstrate that the enzyme converts both cobalt-precorrin-3 and cobalt factor III into the ring-contracted product cobalt-precorrin-4 in high yields, with the latter transformation dependent upon DTT and an intact Fe-S center. Furthermore, the ring contraction process was shown not to involve a change in the oxidation state of the central cobalt ion of the macrocycle.