Dudareva N, D'Auria J C, Nam K H, Raguso R A, Pichersky E
Department of Biology, University of Michigan, Ann Arbor 48109-1048, USA.
Plant J. 1998 May;14(3):297-304. doi: 10.1046/j.1365-313x.1998.00121.x.
Volatile esters impart distinct characteristics to the floral scent of many plants, and are important in attracting insect pollinators. They are also important flavor compounds in fruits. The ester benzylacetate is a major constituent of the floral scent of Clarkia breweri, an annual plant native to California. The enzyme acetyl-CoA:benzylalcohol acetyltransferase (BEAT), which catalyzes the formation of benzylacetate, has been purified from C. breweri petals, and a cDNA encoding this enzyme has been isolated and characterized. The sequence of the 433-residue BEAT protein does not show high similarity to any previously characterized protein, but a 35-residue region from position 135-163 has significant similarity (42-56% identity) to several proteins known or suspected to use an acyl-CoA substrate. E. coli cells expressing C. breweri BEAT produced enzymatically active protein, and also synthesized benzylacetate and secreted it into the medium. Of the different parts of the C. breweri flower, petals contained the majority of BEAT transcripts, and no BEAT mRNA was detected in leaves. The levels of BEAT mRNA in the petals increased as the bud matured, and peaked at anthesis, paralleling changes in BEAT activity. However, three days after anthesis, mRNA levels began a steep decline, whereas BEAT activity remained high for the next two days, suggesting that the BEAT protein is relatively stable.
挥发性酯类赋予许多植物花香独特的特征，在吸引昆虫传粉者方面很重要。它们也是水果中的重要风味化合物。酯类化合物乙酸苄酯是一年生植物布鲁氏克拉克花（Clarkia breweri）花香的主要成分，这种植物原产于加利福尼亚。催化乙酸苄酯形成的乙酰辅酶A：苄醇乙酰转移酶（BEAT）已从布鲁氏克拉克花花瓣中纯化出来，并且编码该酶的cDNA已被分离和鉴定。433个氨基酸残基的BEAT蛋白序列与任何先前鉴定的蛋白质都没有高度相似性，但从第135至163位的35个氨基酸残基区域与几种已知或疑似使用酰基辅酶A底物的蛋白质具有显著相似性（同一性为42 - 56%）。表达布鲁氏克拉克花BEAT的大肠杆菌细胞产生了具有酶活性的蛋白质，并且还合成了乙酸苄酯并将其分泌到培养基中。在布鲁氏克拉克花的不同部位中，花瓣含有大部分BEAT转录本，在叶片中未检测到BEAT mRNA。随着花蕾成熟，花瓣中BEAT mRNA的水平升高，并在开花时达到峰值，这与BEAT活性的变化平行。然而，开花三天后，mRNA水平开始急剧下降，而BEAT活性在接下来的两天内仍保持较高水平，这表明BEAT蛋白相对稳定。
