Prieto Tatiana, Marcon Rodrigo O, Prado Fernanda M, Caires Antonio C F, Di Mascio Paolo, Brochsztain Sergio, Nascimento Otaciro R, Nantes Iseli L
Centro Interdisciplinar de Investigação Bioquímica-CIIB Universidade de Mogi das Cruzes-UMC, Mogi das Cruzes, SP, Brazil.
Phys Chem Chem Phys. 2006 Apr 28;8(16):1963-73. doi: 10.1039/b601671e. Epub 2006 Mar 14.
Microperoxidases (MP) as water-soluble models attract interest to studying the reaction mechanism of peroxidases because these heme peptides are able to form the same enzyme intermediates during the reaction with peroxides. In this work we have demonstrated that the association of Fe(III)MP-9 and Fe(III)MP-11 with CTAB micelles (MP-9/CTAB and MP11/CTAB) provides a microenvironment with an alkaline interface and a hydrophobic core that exhibits peroxidase behavior. This microenvironment shifts positively the redox potential of microperoxidases by approximately 100 mV. tert-Butylhydroperoxide (t-BuOOH) when added to the medium, converted Fe(III)MP-9/CTAB to MP-9/CTAB Compound II, a high valence oxidized intermediate of the heme peptide. Subsequent addition of diphenylacetaldehyde (DPAA) to MP-9/CTAB Compound II regenerated the native form of the enzyme, Fe(III)MP-9/CTAB, what characterizes the occurrence of a peroxidase cycle. Fe(III)MP-9/CTAB regenerated during the peroxidase cycle reacted with residual DPAA in the medium to form Fe(II)MP-9/CTAB, which indicates that both Fe(III)MP-9/CTAB and its oxyferryl form can use aldehydes as reducing agents. According to the determined reduction potential, Fe(III)MP-9 and Fe(III)MP-9/CTAB should be able to oxidize DPAA (reduction potential -630 mV). The reaction of MP-9/CTAB with DPAA produced benzophenone as final product, detected by infrared spectroscopy and mass spectrometry. Interestingly, a significant difference was observed in the benzophenone yield according to the micelle/MP-9 molar ratio.
微过氧化物酶（MP）作为水溶性模型，因其在与过氧化物反应过程中能够形成相同的酶中间体，而吸引了人们对过氧化物酶反应机制的研究兴趣。在这项工作中，我们证明了Fe(III)MP-9和Fe(III)MP-11与十六烷基三甲基溴化铵（CTAB）胶束（MP-9/CTAB和MP11/CTAB）的结合提供了一个具有碱性界面和疏水核心的微环境，该微环境表现出过氧化物酶行为。这种微环境使微过氧化物酶的氧化还原电位正向移动约100 mV。当向介质中加入叔丁基过氧化氢（t-BuOOH）时，Fe(III)MP-9/CTAB转化为MP-9/CTAB化合物II，即血红素肽的高价氧化中间体。随后向MP-9/CTAB化合物II中加入二苯乙醛（DPAA），使酶的天然形式Fe(III)MP-9/CTAB再生，这表征了过氧化物酶循环的发生。在过氧化物酶循环中再生的Fe(III)MP-9/CTAB与介质中残留的DPAA反应形成Fe(II)MP-9/CTAB，这表明Fe(III)MP-9/CTAB及其氧合铁（IV）形式都可以使用醛作为还原剂。根据测定的还原电位，Fe(III)MP-9和Fe(III)MP-9/CTAB应该能够氧化DPAA（还原电位为-630 mV）。通过红外光谱和质谱检测，MP-9/CTAB与DPAA的反应产生二苯甲酮作为最终产物。有趣的是，根据胶束/MP-9摩尔比，观察到二苯甲酮产率存在显著差异。
