Division of Biotechnology, Department of Biology, Friedrich-Alexander-University Erlangen-Nürnberg, D-91054 Erlangen, Germany.
Division of Pharmaceutical Biology, Department of Biology, Friedrich-Alexander-University Erlangen-Nürnberg, D-91058 Erlangen, Germany.
Phytochemistry. 2018 Dec;156:9-19. doi: 10.1016/j.phytochem.2018.08.012. Epub 2018 Aug 29.
PRISEs (progesterone 5β-reductase and/or iridoid synthase-like 1,4-enone reductases) are involved in cardenolide and iridoid biosynthesis. We here investigated a PRISE (rAtSt5βR) from Arabidopsis thaliana, a plant producing neither cardenolides nor iridoids. The structure of rAtSt5βR was elucidated with X-ray crystallography and compared to the known structures of PRISEs from Catharanthus roseus (rCrISY) and Digitalis lanata (rDlP5βR). The three enzymes show a high degree of sequence and structure conservation in the active site. Amino acids previously considered to allow discrimination between progesterone 5β-reductase and iridoid synthase were interchanged among rAtSt5βR, rCrISY and rDlP5βR applying site-directed mutagenesis. Structural homologous substitutions had different effects, and changes in progesterone 5β-reductase and iridoid synthase activity were not correlated in all cases. Our results help to explain fortuitous emergence of metabolic pathways and product accumulation. The fact that PRISEs are found ubiquitously in spermatophytes insinuates that PRISEs might have a more general function in plant metabolism such as, for example, the detoxification of reactive carbonyl species.
PRISEs（孕酮 5β-还原酶和/或裂环烯醚萜合酶样 1,4-二酮还原酶）参与了卡多醇和裂环烯醚萜的生物合成。我们在这里研究了来自拟南芥的 PRISE（rAtSt5βR），这是一种既不产生卡多醇也不产生裂环烯醚萜的植物。通过 X 射线晶体学阐明了 rAtSt5βR 的结构，并与来自长春花（rCrISY）和毛地黄（rDlP5βR）的已知 PRISE 结构进行了比较。这三种酶在活性位点表现出高度的序列和结构保守性。通过定点突变，在 rAtSt5βR、rCrISY 和 rDlP5βR 之间交换了先前被认为可以区分孕酮 5β-还原酶和裂环烯醚萜合酶的氨基酸。结构同源取代具有不同的影响，并且在所有情况下，孕酮 5β-还原酶和裂环烯醚萜合酶活性的变化都没有相关性。我们的结果有助于解释代谢途径和产物积累的偶然出现。PRISEs 在有性植物中普遍存在，这表明 PRISEs 可能在植物代谢中具有更普遍的功能，例如，作为活性羰基物种的解毒剂。
