Ferraro Daniel J, Okerlund Adam, Brown Eric, Ramaswamy S
Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
TAS, Institute for Stem Cell Biology and Regenerative Medicine, GKVK POST, Bangalore 560 065, India.
IUCrJ. 2017 Aug 8;4(Pt 5):648-656. doi: 10.1107/S2052252517008223. eCollection 2017 Sep 1.
Rieske nonheme iron oxygenases (ROs) are a well studied class of enzymes. Naphthalene 1,2-dioxygenase (NDO) is used as a model to study ROs. Previous work has shown how side-on binding of oxygen to the mononuclear iron provides this enzyme with the ability to catalyze stereospecific and regiospecific -dihydroxylation reactions. It has been well documented that ROs catalyze a variety of other reactions, including mono-oxygenation, desaturation, O- and N-dealkylation, sulfoxidation . NDO itself catalyzes a variety of these reactions. Structures of NDO in complex with a number of different substrates show that the orientation of the substrate in the active site controls not only the regiospecificity and stereospecificity, but also the type of reaction catalyzed. It is proposed that the mononuclear iron-activated dioxygen attacks the atoms of the substrate that are most proximal to it. The promiscuity of delivering two products (apparently by two different reactions) from the same substrate can be explained by the possible binding of the substrate in slightly different orientations aided by the observed flexibility of residues in the binding pocket.
里氏非血红素铁加氧酶（ROs）是一类经过充分研究的酶。萘1,2 - 双加氧酶（NDO）被用作研究ROs的模型。先前的研究表明，氧与单核铁的侧位结合赋予了该酶催化立体特异性和区域特异性二羟基化反应的能力。有充分的文献记载，ROs能催化多种其他反应，包括单加氧反应、脱氢反应、O - 和N - 脱烷基反应、硫氧化反应。NDO本身就能催化多种这类反应。NDO与多种不同底物形成复合物的结构表明，底物在活性位点的取向不仅控制区域特异性和立体特异性，还控制催化反应的类型。有人提出，单核铁激活的双氧攻击与其最接近的底物原子。同一底物产生两种产物（显然是通过两种不同反应）的这种混杂性，可以通过结合口袋中残基所观察到的灵活性，底物可能以略有不同的取向结合来解释。
