Functional characterization of enzymes forming volatile esters from strawberry and banana
Functional characterization of enzymes forming volatile esters from strawberry and banana
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DOI：
10.1104/pp.104.042580
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发表时间：
2004-08-01
期刊：
影响因子：
7.4
通讯作者：
Aharoni, A
中科院分区：
文献类型：
--
作者：
Beekwilder, J;Alvarez-Huerta, M;Aharoni, A
挥发性酯是大多数水果的风味成分。其生物合成的最后一步由醇酰基转移酶（AAT）催化，其将醇连接到酰基部分。从野生草莓（Fragaria vesca）和香蕉（Musa sapientum）的果实中分离编码AAT的全长cDNA，并与先前从栽培草莓（Fragaria X ananassa）中分离的SAAT基因进行比较。这些酶在水果风味形成的潜在作用进行了评估。为此，在大肠杆菌中产生重组酶，并分析它们对各种醇和酰基辅酶A底物的活性。当这些活性测定的结果进行了比较的各种成员的酰基转移酶家族的系统发育分析，很明显，底物的偏好不能预测的基础上的序列相似性。此外，重组酶的底物的偏好不一定反映在代表性的酯在相应的水果挥发性配置文件。这表明，一个特定的水果品种的具体配置文件是在很大程度上由前体的供应。为了研究植物体内的醇酰基转移酶的活性，并评估酯生产的代谢工程的潜力，我们产生了过表达SA-AT基因的转基因矮牵牛（矮牵牛）植物。虽然SAAT的表达和相应的酶的活性在转基因植物中很容易检测到，挥发性的配置文件被认为是不变的。将异戊醇喂入转基因系的外植体导致相应的乙酰酯的排放。这证实了当在植物中设计挥发性酯形成时，醇底物的可用性是要考虑的重要参数。
Volatile esters are flavor components of the majority of fruits. The last step in their biosynthesis is catalyzed by alcohol acyltransferases (AATs), which link alcohols to acyl moieties. Full-length cDNAs putatively encoding AATs were isolated from fruit of wild strawberry (Fragaria vesca) and banana (Musa sapientum) and compared to the previously isolated SAAT gene from the cultivated strawberry (Fragaria X ananassa). The potential role of these enzymes in fruit flavor formation was assessed. To this end, recombinant enzymes were produced in Escherichia coli, and their activities were analyzed for a variety of alcohol and acyl-CoA substrates. When the results of these activity assays were compared to a phylogenetic analysis of the various members of the acyltransferase family, it was clear that substrate preference could not be predicted on the basis of sequence similarity In addition, the substrate preference of recombinant enzymes was not necessarily reflected in the representation of esters in the corresponding fruit volatile profiles. This suggests that the specific profile of a given fruit species is to a significant extent determined by the supply of precursors. To study the in planta activity of an alcohol acyltransferase and to assess the potential for metabolic engineering of ester production, we generated transgenic petunia (Petunia hybrida) plants overexpressing the SA-AT gene. While the expression of SAAT and the activity of the corresponding enzyme were readily detected in transgenic plants, the volatile profile was found to be unaltered. Feeding of isoamyl alcohol to explants of transgenic lines resulted in the emission of the corresponding acetyl ester. This confirmed that the availability of alcohol substrates is an important parameter to consider when engineering volatile ester formation in plants.