Sengupta Debashree, Naik Dhiraj, Reddy Attipalli R
Department of Environmental Biotechnology and Ecological Sciences, Indian Institute of Advanced Research, Gandhinagar 382007, Gujarat, India; Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
Department of Environmental Biotechnology and Ecological Sciences, Indian Institute of Advanced Research, Gandhinagar 382007, Gujarat, India.
J Plant Physiol. 2015 May 1;179:40-55. doi: 10.1016/j.jplph.2015.03.004. Epub 2015 Mar 20.
The aldo-keto reductase (AKR) superfamily comprises of a large number of primarily monomeric protein members, which reduce a broad spectrum of substrates ranging from simple sugars to potentially toxic aldehydes. Plant AKRs can be broadly categorized into four important functional groups, which highlight their roles in diverse plant metabolic reactions including reactive aldehyde detoxification, biosynthesis of osmolytes, secondary metabolism and membrane transport. Further, multiple overlapping functional aspects of plant AKRs including biotic and abiotic stress defense, production of commercially important secondary metabolites, iron acquisition from soil, plant-microbe interactions etc. are discussed as subcategories within respective major groups. Owing to the broad substrate specificity and multiple stress tolerance of the well-characterized AKR4C9 from Arabidopsis thaliana, protein sequences of all the homologues of AKR4C9 (A9-like proteins) from forty different plant species (Phytozome database) were analyzed. The analysis revealed that all A9-like proteins possess strictly conserved key catalytic residues (D-47, Y-52 and K-81) and belong to the pfam00248 and cl00470 AKR superfamilies. Based on structural homology of the three flexible loops of AKR4C9 (Loop A, B and C) responsible for broad substrate specificity, A9-like proteins found in Brassica rapa, Phaseolus vulgaris, Cucumis sativus, Populus trichocarpa and Solanum lycopersicum were predicted to have a similar range of substrate specificity. Thus, plant AKRs can be considered as potential breeding targets for developing stress tolerant varieties in the future. The present review provides a consolidated update on the current research status of plant AKRs with an emphasis on important functional aspects as well as their potential future prospects and an insight into the overall structure-function relationships of A9-like proteins.
醛酮还原酶（AKR）超家族由大量主要为单体的蛋白质成员组成，这些成员可还原从单糖到潜在有毒醛类等广泛的底物。植物AKR可大致分为四个重要的功能组，这突出了它们在多种植物代谢反应中的作用，包括活性醛解毒、渗透调节物质的生物合成、次生代谢和膜运输。此外，还讨论了植物AKR的多个重叠功能方面，包括生物和非生物胁迫防御、商业上重要的次生代谢产物的产生、从土壤中获取铁、植物-微生物相互作用等，作为各自主要组内的子类别。由于拟南芥中已得到充分表征的AKR4C9具有广泛的底物特异性和多重胁迫耐受性，因此对来自四十种不同植物物种（植物基因组数据库）的AKR4C9所有同源物（A9样蛋白）的蛋白质序列进行了分析。分析表明，所有A9样蛋白都具有严格保守的关键催化残基（D-47、Y-52和K-81），并属于pfam00248和cl00470 AKR超家族。基于负责广泛底物特异性的AKR4C9三个柔性环（环A、B和C）的结构同源性，预测在甘蓝型油菜、菜豆、黄瓜、毛果杨和番茄中发现的A9样蛋白具有相似范围的底物特异性。因此，植物AKR可被视为未来培育耐胁迫品种的潜在育种目标。本综述提供了关于植物AKR当前研究现状的综合更新，重点关注重要的功能方面及其潜在的未来前景，并深入了解A9样蛋白的整体结构-功能关系。
