Molecular characteristics of isoprene synthase and its control effects on isoprene emissions from tropical trees
Molecular characteristics of isoprene synthase and its control effects on isoprene emissions from tropical trees
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异戊二烯合酶的分子特征及其对热带树木异戊二烯排放的控制作用
DOI：
10.1007/s10265-022-01418-4
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发表时间：
2022
影响因子：
2.8
通讯作者：
Inafuku Masashi
中科院分区：
文献类型：
--
作者：
Oku Hirosuke;Mutanda Ishmael;Inafuku Masashi
植物异戊二烯的排放速率可以用光强和叶温的函数来模拟，而G-93公式是应用最广泛的算法。异戊二烯是由异戊二烯合成酶(ISPs)生物合成的，并立即从叶片中释放出来。ISPs的酶动力学和底物可利用性是短期控制异戊二烯排放的重要因素。因此，假设G-93的参数可能与Ispss的动力学有关，但目前还没有关于这两个参数之间关系的数据。本研究从热带树木中克隆了6个isps基因，对其性质进行了鉴定，并研究了isps的酶动力学与G-93参数之间的关系。IspSKm的酶动力学与用于定义异戊二烯排放的温度依赖性的G93的参数CT1之间存在负相关。然而，ISPS的性能常数(kcat/Km)仅与CT1呈轻微的正相关，表明ISPS的酶动力学对控制异戊二烯排放的温度响应的意义有限。用分子动力学模拟进一步阐明了ISPs的分子结构，重点是6α-螺旋束中的活性部位。B。对ISPS的酶-底物复合体的模拟。在螺旋F(E383)上预测了一个新的金属结合域，并在A-C环上预测了催化基序FXRDRLXE，该基序可能涉及二甲基烯丙基二磷酸(DMADP)的去质子化形成碳正离子。值得注意的是，在金属离子与DMADP结合后，发现活性位关闭机制涉及H-α1螺旋的构象变化和6个α-螺旋束从松散到紧密的转变，以调节活性口袋的大小。热带树木Isps的特征有助于解释热带地区的区域性异戊二烯排放。
The isoprene emission rate from plants is simulated by a function of light intensity and leaf temperature, and the G-93 formula is the most extensively applied algorithm for this purpose. Isoprene is biosynthesized by the enzyme isoprene synthase (IspS), and instantly emitted from the leaf. Enzyme kinetics of IspS and substrate availability are important factors involved in the short-term leaf-level control of isoprene emissions. It is thus assumed that the parameters of G-93 may correlate with the kinetics of IspSs, however, at present there is no data available on the relationship between these two parameters. In this investigation, six IspS genes from tropical trees were cloned, their properties characterized, and the relationship between the enzyme kinetics of IspSs and the parameters of G-93 examined. There was a negative correlation between the enzyme kinetics of IspSKmand parameterCT1of G93, which is used to define the temperature dependency of isoprene emissions. However, performance constant of IspS (kcat/Km) only showed slight positive correlation withCT1.suggesting that the enzyme kinetics of IspS has limited significance in controlling the temperature response of isoprene emissions. The molecular structure of IspS was further elucidated using a molecular dynamics simulation with a focus on the active site in the 6 α-helices bundle. The simulation of the enzyme–substrate complex of IspS fromB. variegatapredicted a new metal binding domain in helix F (E383) and catalytic motif FXRDRLXE in the A-C loop that could involve the deprotonation of dimethylallyl diphosphate (DMADP) to form a carbocation. Notably, after the binding of a metal ion and DMADP, the active-site closure mechanism was found to involve conformational alterations in the helix H-α1 and transition from a loose to tight enclosure of the 6 α-helices bundles to tune the active pocket size. The characteristics identified for the IspSs from tropical trees could help to explain regional isoprene emissions in tropical areas.