A synthetic model for the NO-inactivated form of nitrile hydratase
A synthetic model for the NO-inactivated form of nitrile hydratase
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DOI：
10.1021/ja981117e
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发表时间：
1998-10-28
影响因子：
15
通讯作者：
Kovacs, JA
中科院分区：
文献类型：
--
作者：
Schweitzer, D;Ellison, JJ;Kovacs, JA
一氧化氮（NO）1已被证明在医学和生物学中具有许多重要功能，包括血压控制，神经传递和抑制肿瘤生长。2，3最近，NO被发现在金属酶腈水合酶（NHase）中发挥调节作用4，5通过可逆地结合到其铁活性位点。6腈水合酶7 -12是非血红素、低自旋的含Fe（III）的微生物酶，其促进腈水合为酰胺。三个面半胱氨酸、两个顺式肽氮11和一个氢氧化物13以其活性形式（NHlt）连接铁。在黑暗中储存的全细胞细菌样品中产生无活性的NO结合形式（NHdk）。14活性在暴露于光后恢复。4-6在1853 cm-1处的IR带的存在表明NO与铁位点配位。14自旋捕获4和定量NO滴定实验6表明，在光活化过程中，每个铁释放一个NO。最初的研究5，14表明，NHdk含有Fe（II）-NO物种。然而，灭活NHdk的EPR沉默15与该提议不一致。最近来自红球菌属物种N-771的NHdk的X射线结构16显示，两个连接的半胱氨酸已被氧化成亚磺酸盐和亚磺酸盐基团。然而，没有提到本研究中使用的晶体（a）是否可以被光解再活化或（B）是否显示NHdk的νNO特征。通过共振拉曼，在来自红球菌属R312的NHlt中未检测到亚磺酸酯基团。17在此，我们报道了一种合成的、NO结合的、双（硫醇盐）连接的铁络合物，其与NHdk铁位点的性质密切匹配，尽管不存在亚磺酸酯基团。
Nitric oxide (NO) 1 has been shown to perform a number of important functions in medicine and biology, including blood pressure control, neurotransmission, and inhibition of tumor growth. 2, 3 More recently, NO was found to play a regulatory role in the metalloenzyme nitrile hydratase (NHase) 4, 5 by reversibly binding to its iron active site. 6 Nitrile hydratases7-12 are nonheme, low-spin Fe (III)-containing microbial enzymes which promote the hydration of nitriles to amides. Three facial cysteinates, two cis peptide nitrogens, 11 and a hydroxide13 ligate the iron in its active form (NHlt). An inactive, NO-bound form (NHdk) is generated in whole cell bacterial samples stored in the dark. 14 Activity is restored upon exposure to light. 4-6 The presence of an IR band at 1853 cm-1 suggests that NO coordinates to the iron site. 14 Spin-trapping4 and quantitative NO titration experiments6 show that one NO is released per iron during photoactivation. Initial studies5, 14 suggested that NHdk contained an Fe (II)-NO species. The EPR silence15 of inactivated NHdk was, however, inconsistent with this proposal. A recent X-ray structure16 of NHdk from Rhodococcus sp. N-771 showed that two of the ligated cysteinates had been oxidized to sulfenate and sulfinate groups. However, it was not mentioned whether the crystals used in this study (a) could be photolytically reactivated or (b) displayed the νNO characteristic of NHdk. Sulfinate groups are not detected, by resonance Raman, in NHlt from Rhodococcus sp. R312. 17 Herein, we report a synthetic, NO-bound, bis-(thiolate)-ligated iron complex which closely matches the properties of the NHdk iron site, despite the absence of sulfinate groups.