Oxy intermediates of homoprotocatechuate 2,3-dioxygenase: facile electron transfer between substrates.
Oxy intermediates of homoprotocatechuate 2,3-dioxygenase: facile electron transfer between substrates.
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DOI：
10.1021/bi201436n
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发表时间：
2011-11-29
期刊：
影响因子：
2.9
通讯作者：
Lipscomb, John D.
中科院分区：
文献类型：
--
作者：
Mbughuni, Michael M.;Chakrabarti, Mrinmoy;Hayden, Joshua A.;Meier, Katlyn K.;Dalluge, Joseph J.;Hendrich, Michael P.;Muenck, Eckard;Lipscomb, John D.
底物高原儿茶酸（HPCA）和O2在相邻的配位位点与高原儿茶酸2，3-双加氧酶（FeHPCD）的FeII结合。提出了通过铁将电子从HPCA转移到O2以激活底物彼此反应以引发芳环裂解。在这里，快速冷冻淬灭方法用于捕获和光谱表征FeHPCD和变体His 200 Asn（FeHPCD-HPCA和H200 N-HPCA）与O2的HPCA复合物反应中的中间体。O2与H200 N-HPCA（H200 NInt 1HPCA）混合后，在20 ms内形成蓝色中间体。平行模式EPR和穆斯堡尔谱表明，该中间体含有高自旋FeIII（S=5/2）反铁磁耦合到自由基（SR=1/2），产生S=2状态。总之，光学和穆斯堡尔谱的中间支持分配的自由基作为HPCA半醌，这意味着氧是绑定作为（氢）过氧配体。H200 NInt 1HPCA在接下来的2秒内衰变，可能通过Fe II中间体（H200 NInt 2 HPCA），以产生产物和静息Fe II酶。FeHPCD-HPCA与O2的反应导致快速形成无色Fe II中间体（FeHPCDInt 1HPCA）。该物种在1秒内衰变，产生产物和静息酶。从semiquinone的发色团或FeHPCDInt 1HPCA中的自旋耦合物种的证据的情况下表明，它是一个中间体发生后，O2激活和攻击。FeHPCDInt 1HPCA和H200 NInt 2 HPCA相似的穆斯堡尔参数表明它们是相似的中间体。结果表明，电子转移从基板到O2通过铁确实发生导致芳环断裂。
Substrates homoprotocatechuate (HPCA) and O2 bind to the FeII of Homoprotocatechuate 2,3-dioxygenase (FeHPCD) in adjacent coordination sites. Transfer of an electron(s) from HPCA to O2 via the iron is proposed to activate the substrates for reaction with each other to initiate aromatic ring cleavage. Here, rapid-freeze-quench methods are used to trap and spectroscopically characterize intermediates in the reactions of the HPCA complexes of FeHPCD and the variant His200Asn (FeHPCD-HPCA and H200N-HPCA) with O2. A blue intermediate forms within 20 ms after mixing O2 with H200N-HPCA (H200NInt1HPCA). Parallel mode EPR and Mössbauer spectroscopies show that this intermediate contains high-spin FeIII (S=5/2) antiferromagnetically coupled to a radical (SR=1/2) to yield an S=2 state. Together, optical and Mössbauer spectra of the intermediate support assignment of the radical as an HPCA semiquinone, implying that oxygen is bound as a (hydro)peroxo ligand. H200NInt1HPCA decays over the next 2 s, possibly through an FeII intermediate (H200NInt2HPCA), to yield product and the resting FeII enzyme. Reaction of FeHPCD-HPCA with O2 results in rapid formation of a colorless FeII intermediate (FeHPCDInt1HPCA). This species decays within 1 s to yield the product and the resting enzyme. The absence of a chromophore from a semiquinone or evidence for a spin-coupled species in FeHPCDInt1HPCA suggests it is an intermediate occurring after O2 activation and attack. The similar Mössbauer parameters for FeHPCDInt1HPCA and H200NInt2HPCA suggest these are similar intermediates. The results show that electron transfer from the substrate to the O2 via the iron does occur leading to aromatic ring cleavage.
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影响因子：
15
作者：
LYNCH, MW;VALENTINE, M;HENDRICKSON, DN
通讯作者：
HENDRICKSON, DN
影响因子：
3
作者：
Fielding, Andrew J.;Kovaleva, Elena G.;Farquhar, Erik R.;Lipscomb, John D.;Que, Lawrence, Jr.
通讯作者：
Que, Lawrence, Jr.
DOI：
10.1039/c39840001170
发表时间：
1984-01-01
影响因子：
--
作者：
CHEDEKEL, MR;LAND, EJ;TRUSCOTT, TG
通讯作者：
TRUSCOTT, TG
影响因子：
2.9
作者：
Groce, SL;Miller-Rodeberg, MA;Lipscomb, JD
通讯作者：
Lipscomb, JD
影响因子：
15
作者：
Gunderson, William A.;Zatsman, Anna I.;Emerson, Joseph P.;Farquhar, Erik R.;Que, Lawrence, Jr.;Lipscomb, John D.;Hendrich, Michael P.
通讯作者：
Hendrich, Michael P.