Kim Bong-Gyu, Jung Bo-Ra, Lee Youngshim, Hur Hor-Gil, Lim Yoongho, Ahn Joong-Hoon
Bio/Molecular Informatics Center, Department of Molecular Biotechnology, Konkuk University, Seoul 143-701, Korea.
J Agric Food Chem. 2006 Feb 8;54(3):823-8. doi: 10.1021/jf0522715.
O-Methylation, commonly found in synthesis of secondary metabolites of plants and micro-organisms, appears to transfer a methyl group to the hydroxyl group of the recipient which increases the hydrophobicity of the recipient. O-Methyltransferase (OMT), , was isolated and characterized from Streptomyces avermitilis MA-4680. Its amino acid sequence showed 68% similarity with antibiotic C-1027 OMT and 53% similarity with the carminomycin 4-OMT. was expressed in E. coli as a His-tag fusion protein and showed that the methyl was transferred onto the 7-hydroxyl group of the isoflavones, daidzein and genistein, and the flavones, kaempferol and quercetin, as well as the flavanone naringenin. NMR and liquid chromatography-mass spectrometry were used to confirm the location of the methyl group on the recipient compound of naringenin, which was biotransformed into sakuranetin by E. coli transformant expressing (E. coli Sa-2). Therefore, E. coli Sa-2 would be used for the synthesis of the antifungal flavonoid, sakuranetin, through biotransformation.
O-甲基化常见于植物和微生物次生代谢产物的合成过程中，它似乎是将一个甲基转移到受体的羟基上，从而增加了受体的疏水性。从阿维链霉菌MA-4680中分离并鉴定出了O-甲基转移酶（OMT）。其氨基酸序列与抗生素C-1027 OMT的相似度为68%，与洋红霉素4-OMT的相似度为53%。该酶在大肠杆菌中作为His标签融合蛋白表达，并表明甲基转移到了异黄酮黄豆苷元和染料木黄酮、黄酮山奈酚和槲皮素以及黄烷酮柚皮素的7-羟基上。利用核磁共振和液相色谱-质谱联用技术确定了柚皮素受体化合物上甲基的位置，表达该酶的大肠杆菌转化体（大肠杆菌Sa-2）将柚皮素生物转化为樱花素。因此，大肠杆菌Sa-2可用于通过生物转化合成抗真菌类黄酮樱花素。
