Wu Shuiqin, Watanabe Naoharu, Mita Satoru, Ueda Yoshihiro, Shibuya Masaaki, Ebizuka Yutaka
Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
J Biosci Bioeng. 2003;96(2):119-28.
Rosa chinensis var. spontanea predominantly emits 1,3,5-trimethoxybenzene together with methyleugenol and isomethyleugenol as minor floral scent compounds. Two O-methyltransferases (OMTs), designated as RcOMT1 and RcOMT2, were isolated from rose flower petals using homology-based screening strategies. RcOMT1 efficiently methylated eugenol and isoeugenol to yield volatile methyleugenol and isomethyleugenol, respectively. Furthermore, the mRNA transcripts of RcOMT1 were highly expressed in floral organs and the expression pattern coincided with intracellular content changes of methyleugenol and isomethyleugenol in rose flowers. In contrast, RcOMT2, which shows 94% similarity with caffeic acid O-methyltransferase (COMT) of Prunus amygdalus, was expressed in all tissues tested and had the highest activity with caffeic acid, a typical substrate for COMT. However, this COMT-like OMT also showed some degrees of activity with all three putative precursors of 1,3,5-trimethoxybenzene.
野蔷薇主要释放1,3,5-三甲氧基苯，同时释放少量的甲基丁香酚和异甲基丁香酚作为花香成分。利用基于同源性的筛选策略，从玫瑰花瓣中分离出两种O-甲基转移酶（OMT），分别命名为RcOMT1和RcOMT2。RcOMT1能有效地将丁香酚和异丁香酚甲基化，分别生成挥发性的甲基丁香酚和异甲基丁香酚。此外，RcOMT1的mRNA转录本在花器官中高度表达，其表达模式与玫瑰花中甲基丁香酚和异甲基丁香酚的细胞内含量变化一致。相比之下，RcOMT2与扁桃酸的咖啡酸O-甲基转移酶（COMT）有94%的相似性，在所有测试组织中均有表达，对咖啡酸（COMT的典型底物）具有最高活性。然而，这种类似COMT的OMT对1,3,5-三甲氧基苯的所有三种假定前体也表现出一定程度的活性。
