Nitrophorins as Multifunctional Heme Enzymes: The Peroxidase Activity

这个无机、生物无机和有机金属化学项目的奖项支持亚利桑那大学的F. Ann Walker教授对硝基磷（NPs）过氧化物酶活性的研究。这些铁血红蛋白来自吸血昆虫长角红蝇的唾液，已知可以将NO隔绝在唾液腺中，并在被咬时将其释放到受害者的组织中。初步研究结果表明，这些蛋白质还能与过氧化氢或过氧乙酸（PAA）反应，氧化过氧化物酶的典型底物，以及重要的生物效应物去甲肾上腺素。被称为化合物I的高价中间体是在H2O2或PAA与NP快速混合后形成的。在不同的pH值下可以看到化合物I的两种形式；在高pH值下观察到典型的化合物I光谱，而在低pH值下观察到不同的信号，这是过氧化物酶的新信号，但以前在模型血红素复合物中看到过。导致这些信号出现的因素，它们消失形成蛋白质的酪氨酸自由基，以及它们随后与有机底物的反应性，将在本项目中进行研究。将开发一门关于过氧化物酶和加氧酶的课程，提供给亚利桑那大学化学、生物化学和药物化学专业的本科生和研究生，课程材料将在WWW上提供给其他人。过氧化物及其氧化反应在化学和生物系统以及工业环境中都很重要。过氧化氢（和有机过酸）与过渡金属反应的机理与大规模的化学和生物化学有关，也与植物和动物中产生有害活性氧（ROS）的反应有关。研究新型铁血红素酶的高价反应活性将有助于深入了解稳定每种高价化合物I的因素及其随后与有机底物的反应性。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports work by Professor F. Ann Walker at the University of Arizona to probe the peroxidase activity of the nitrophorins (NPs). These ferriheme proteins, from the saliva of the blood-sucking insect Rhodnius prolixus, are known to sequester NO in the salivary glands and release it into the tissues of the victim during a bite. Preliminary findings have shown that these proteins also react with hydrogen peroxide or peroxyacetic acid (PAA) to oxidize typical substrates of peroxidase enzymes, as well as the important biological effector norepinephrine. The high-valent intermediate known as Compound I is formed after rapid mixing of H2O2 or PAA with NP. Two forms of Compound I are seen at different pH values; at high pH the typical Compound I spectrum is observed, while at low pH a different signal, novel for peroxidase enzymes, but previously seen in model heme complexes, is observed. The factors that cause the appearance of each of these signals, their disappearance to form tyrosyl radicals of the protein, and their subsequent reactivity with organic substrates, will be investigated in this project. A course on peroxidase and oxygenase enzymes will be developed and offered to undergraduate and graduate students in Chemistry, Biochemistry and Pharmaceutical Chemistry at the University of Arizona, and the course materials will be made available to others on the WWW.Peroxides and their oxidation reactions are important in chemical and biological systems and in industrial settings. The mechanisms of hydrogen peroxide (and organic peracid) reaction with transition metals are relevant to large scale chemistry and biochemistry, as well as to the reactions that produce deleterious Reactive Oxygen Species (ROS) in plants and animals. Investigation of the high valent reactivity of the novel ferriheme enzymes to be studied will provide insight into the factors that stabilize each of the high valent Compound I species and their subsequent reactivity with organic substrates.