Department of Chemistry, Stanford University, Stanford, California 94305, USA.
J Biol Chem. 2013 Apr 19;288(16):11233-41. doi: 10.1074/jbc.M112.415570. Epub 2013 Feb 28.
We employ error-corrected density functional theory methods to map out the dependence of reactivity on substrate position for SyrB2, a member of a family of non-heme iron halogenases and hydroxylases that are only reactive toward amino acid substrates delivered via prosthetic phosphopantetheine arms. For the initial hydrogen abstraction step, the inherent flexibility of the phosphopantetheine molecule weakens the position dependence for both the native substrate (threonine for SyrB2) and alternative substrates. Over a 5 Å window of substrate positions, the tethered hydrogen abstraction step proceeds with nearly identical activation energies and donor-acceptor distances in the transition state. The propensity of a particular substrate toward halogenation or hydroxylation is found to depend strongly on the substrate placement following hydrogen abstraction, with deeper substrate delivery into the active (for native substrates) site favoring halogenation and shallower substrate delivery favoring hydroxylation.
我们采用纠错密度泛函理论方法来描绘 SyrB2 的反应性对底物位置的依赖性，SyrB2 是一组非血红素铁卤化酶和羟化酶的成员，这些酶仅对通过 prosthetic phosphopantetheine 臂递送的氨基酸底物有反应性。对于初始的氢提取步骤，磷酸泛酰巯基乙胺分子的固有灵活性削弱了天然底物（SyrB2 的苏氨酸）和替代底物的位置依赖性。在底物位置的 5 Å 窗口内，连接的氢提取步骤在过渡态中具有几乎相同的活化能和供体-受体距离。发现特定底物发生卤化或羟化的倾向强烈取决于氢提取后的底物位置，更深的底物进入活性（天然底物）位点有利于卤化，而更浅的底物进入有利于羟化。
