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首页> 外文期刊>Biochemistry >Unique Biochemical and Sequence Features Enable BluB To Destroy Flavin and Distinguish BluB from the Flavin Monooxygenase Superfamily
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Unique Biochemical and Sequence Features Enable BluB To Destroy Flavin and Distinguish BluB from the Flavin Monooxygenase Superfamily

机译：独特的生化和序列特征使Blub能够破坏黄素并将Blub与Flavin单氧基酶超家族区分开

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摘要

Vitamin B-12 (cobalamin) is an essential micronutrient for humans that is synthesized by only a subset of bacteria and archaea. The aerobic biosynthesis of 5,6-dimethylbenzimidazole, the lower axial ligand of cobalamin, is catalyzed by the "flavin destructase" enzyme BluB, which fragments reduced flavin mononucleotide following its reaction with oxygen to yield this ligand. BluB is similar in sequence and structure to members of the flavin oxidoreductase superfamily, yet the flavin destruction process has remained elusive. Using stopped-flow spectrophotometry, we find that the flavin destructase reaction of BluB from Sinorhizobium meliloti is initiated with canonical flavin-O-2 chemistry. A C4a-peroxyflavin intermediate is rapidly formed in BluB upon reaction with O-2, and has properties similar to those of flavin-dependent hydroxylases. Analysis of reaction mixtures containing flavin analogues indicates that both formation of the C4a-peroxyflavin and the subsequent destruction of the flavin to form 5,6-dimethylbenzimidazole are influenced by the electronic properties of the flavin isoalloxazine ring. The flavin destruction phase of the reaction, which results from the decay of the C4a-peroxyflavin intermediate, occurs more efficiently at pH 7.5. Furthermore, the BluB mutants D32N and S167G are specifically impaired in the flavin destruction phase of the reaction; nevertheless, both form the C4a-peroxyflavin nearly quantitatively. Coupled with a phylogenetic analysis of BluB and related flavin-dependent enzymes, these results demonstrate that the BluB flavin destructase family can be identified by the presence of active site residues D32 and S167.
机译：维生素B-12（Cobalamin）是仅由细菌和古代的子集合合成的人类的必需微量营养素。 5,6-二甲基双咪唑的有氧生物合成，钴胺蛋白的下轴向配体，由“黄素破坏酶”酶BLUB催化，该酶酶酶使其与氧反应后的黄蛋白单核苷酸以产生该配体。 Blub序列和结构与黄素氧化还原酶超家族的成员相似，但Flavin破坏过程仍然难以捉摸。使用停止流量分光光度法，我们发现，用Canonical Flavin-O-2化学引发来自Sinorhizobium Meliloti的Flavin破坏酶反应。在与O-2反应时，在BLUB中快速形成C4A-过氧吡啶中间体，并且具有与黄素依赖性羟基酶类似的性质。含有黄素类似物的反应混合物的分析表明，C4A-过氧吡喃嗪的形成和随后的黄素破坏形成5,6-二甲基双咪唑的反应性受氟异唑嗪环的电子性质的影响。来自C4A-过氧吡啶中间体的衰减产生的反应的黄素破坏阶段，在pH＆gt中更有效地发生。7.5。此外，Blub突变体D32N和S167G在反应的黄液破坏阶段特别损害;然而，两者都与C4A-Peroxyflavin几乎定量形成。结合Blub的系统发育分析和相关的Flavin依赖性酶，这些结果表明，Blub Flavin破坏性酶系列可以通过活性位点残留物D32和S167的存在来鉴定。

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  • 来源
    《Biochemistry》 |2018年第11期|共10页
  • 作者

    Hazra Amrita B.; Ballou David P.; Tag Michiko E.;

  • 作者单位

    Univ Calif Berkeley Dept Plant &

    Microbial Biol Berkeley CA 94720 USA;

    Univ Michigan Dept Biol Chem Ann Arbor MI 48109 USA;

    Univ Calif Berkeley Dept Plant &

    Microbial Biol Berkeley CA 94720 USA;

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  • 正文语种 eng
  • 中图分类 生物化学;
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