Structure activity studies with xenobiotic substrates using carboxylesterases isolated from Arabidopsis thaliana
Structure activity studies with xenobiotic substrates using carboxylesterases isolated from Arabidopsis thaliana
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DOI：
10.1016/j.phytochem.2006.12.014
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发表时间：
2007-03-01
期刊：
影响因子：
3.8
通讯作者：
Edwards, Robert
中科院分区：
文献类型：
--
作者：
Cummins, Ian;Landrum, Marie;Edwards, Robert
羧酸酯酶(CXE)催化外源化合物和天然产物的水解，从根本上改变它们的生物活性。虽然动物CXE的底物选择性已经得到了很好的研究，例如猪肝酯酶(PLE)，但植物中的各种酶还没有被定义，它们的活性也还没有确定。以拟南芥为来源，克隆、表达了α/β水解酶AtCXE家族中具有代表性的5个成员，并对纯化的重组蛋白进行了与异源底物的酯酶活性测定。两个成员AtCXE5和AtCXE18被发现是活性羧酸酯酶，尽管AtCXE5被证明是一种高度不稳定的可溶性蛋白质。ATCXE18和以前表征的拟南芥S甲酰基谷胱甘肽水解酶(AtSFGH)与一系列基于甲基伞形酮的酯进行了比较，其中的酰基部分随着大小和构象的变化而变化。用相同的系列测定了来自拟南芥植物的粗酯酶制剂，并与常用的PLE得到的结果进行了比较。对于直链酯，AtCXE18的行为类似于PLE，但拟南芥水解酶对支链酰基成分的耐受性不如哺乳动物酶。虽然没有一种酶制剂准确地反映了用拟南芥蛋白粗提物测定的所有活性，但植物酶被证明比PLE在预测空间约束更多的酯的水解方面更有用。(C)2006爱思唯尔有限公司。保留所有权利。
Carboxylesterases (CXEs) catalyse the hydrolysis of xenobiotics and natural products radically altering their biological activities. Whereas the substrate selectivity of animal CXEs, such as porcine liver esterase (PLE) have been well studied, the respective enzymes in plants have yet to be defined and their activities determined. Using Arabidopsis thaliana (At) as a source, five representative members of the alpha/beta hydrolase AtCXE family of proteins have been cloned, expressed and the purified recombinant proteins assayed for esterase activity with xenobiotic substrates. Two members, AtCXE5 and AtCXE18 were found to be active carboxylesterases, though AtCXE5 proved to be highly unstable as a soluble protein. AtCXE18 and the previously characterised S-formylglutathione hydrolase from Arabidopsis (AtSFGH) were assayed against a series of esters based on methylumbelliferone in which the acyl moiety was varied with respect to size and conformation. The same series was used to assay crude esterase preparation from Arabidopsis plants and the results compared with those obtained with the commonly used PLE. With straight chain esters, AtCXE18 behaved like PLE, but the Arabidopsis hydrolases proved less tolerant of branched chain acyl components than the mammalian enzyme. While none of the enzyme preparations accurately reflected all the activities determined with crude Arabidopsis protein extracts, the plant enzymes proved more useful than PLE in predicting the hydrolysis of the more sterically constrained esters. (c) 2006 Elsevier Ltd. All rights reserved.