Li Huaijun Michael, Rotter David, Hartman Thomas G, Pak Fulya E, Havkin-Frenkel Daphna, Belanger Faith C
Department of Plant Biology and Pathology and The Biotechnology Center for Agriculture & the Environment, Cook College, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901, USA.
Plant Mol Biol. 2006 Jun;61(3):537-52. doi: 10.1007/s11103-006-0029-4.
The biosynthesis of many plant secondary compounds involves the methylation of one or more hydroxyl groups, catalyzed by O-methyltransferases (OMTs). Here, we report the characterization of two OMTs, Van OMT-2 and Van OMT-3, from the orchid Vanilla planifolia Andrews. These enzymes catalyze the methylation of a single outer hydroxyl group in substrates possessing a 1,2,3-trihydroxybenzene moiety, such as methyl gallate and myricetin. This is a substrate requirement not previously reported for any OMTs. Based on sequence analysis these enzymes are most similar to caffeic acid O-methyltransferases (COMTs), but they have negligible activity with typical COMT substrates. Seven of 12 conserved substrate-binding residues in COMTs are altered in Van OMT-2 and Van OMT-3. Phylogenetic analysis of the sequences suggests that Van OMT-2 and Van OMT-3 evolved from the V. planifolia COMT. These V. planifolia OMTs are new instances of COMT-like enzymes with novel substrate preferences.
许多植物次生化合物的生物合成涉及一个或多个羟基的甲基化，由O-甲基转移酶（OMT）催化。在此，我们报道了从兰花香草（Vanilla planifolia Andrews）中鉴定出的两种OMT，即Van OMT-2和Van OMT-3。这些酶催化具有1,2,3-三羟基苯部分的底物（如没食子酸甲酯和杨梅素）中单个外部羟基的甲基化。这是此前任何OMT均未报道过的底物要求。基于序列分析，这些酶与咖啡酸O-甲基转移酶（COMT）最为相似，但它们对典型的COMT底物活性可忽略不计。COMT中12个保守的底物结合残基中有7个在Van OMT-2和Van OMT-3中发生了改变。序列的系统发育分析表明，Van OMT-2和Van OMT-3是从香草COMT进化而来的。这些香草OMT是具有新底物偏好的类COMT酶的新实例。
