Substrate selectivity of an isolated enoyl reductase catalytic domain from an iterative highly reducing fungal polyketide synthase reveals key components of programming
作者:Douglas M. Roberts、Christoph Bartel、Alan Scott、David Ivison、Thomas J. Simpson、Russell J. Cox
DOI:10.1039/c6sc03496a
日期:——
A cis-acting enoyl reductase (ER) catalytic domain was isolated from a fungal highly reducing iterative polyketidesynthase (HR-iPKS) for the first time and studied in vitro. The ER from the squalestatin tetraketide synthase forms a discrete dimeric protein in solution. The ER shows broad substrate selectivity, reducing enoyl species including both natural and unnatural substrates. Pantetheine-bound
首次从真菌高还原性重复聚酮合酶(HR-iPKS)中分离出顺式烯酰还原酶(ER)催化结构域并进行体外研究。来自角鲨他汀四酮化合物合酶的 ER 在溶液中形成离散的二聚体蛋白质。ER 显示出广泛的底物选择性,可减少烯酰基物质,包括天然和非天然底物。泛硫氨酸结合底物硫醇酯的反应速度比相应的 SNAC 硫醇酯快得多。非天然底物包括Z-烯烃、2-乙基烯烃和五肽。底物的甲基化改变了 ER 的活性,使得 2,4-二甲基辛-2-烯酰基底物适合活性位点但不能被还原。开发了一种新的基于 NMR 的测定法,用于直接观察 NADPH 辅因子 4' 位置以及底物 C-2 和 C-3 位置的立体化学偏好。该测定表明,真菌 iPKS ER 催化的反应在立体化学上与脊椎动物 FAS (vFAS) 在辅因子 4' 位和底物 3 位的反应相同,但完整 SQTKS 所表现出的高立体选择性消失,导致在2 位对分离的 ER 没有选择性。ER
Structural analysis of the dual-function thioesterase SAV606 unravels the mechanism of Michael addition of glycine to an α,β-unsaturated thioester
(R)-N-carboxymethyl-3-aminobutyric acid. We also determined the crystalstructures of SAV606 both in ligand-free form at 2.4 Åresolution and in complex with (R)-N-carboxymethyl-3-aminobutyric acid at 2.0 Åresolution. We found that SAV606 adopts an α/β hotdog fold and has an activesite at the dimeric interface. Examining the complexed structure, we noted that the substrate-binding loop comprising Tyr-53-Asn-61