Knogge W, Weissenböck G
Eur J Biochem. 1984 Apr 2;140(1):113-8. doi: 10.1111/j.1432-1033.1984.tb08073.x.
An O-methyltransferase catalyzing the transfer of the methyl group of S-adenosyl-L-methionine to the A-ring 7-hydroxyl group of vitexin 2"-O-rhamnoside has been isolated from oat primary leaves and purified 180-fold by protein fractionation with (NH4)2SO4 and chromatography on DEAE-cellulose and S-adenosyl-L-homocysteine-sepharose. Km values for S-adenosyl-L-methionine and the flavonoid substrate were 1.6 microM and 15 microM, respectively. The lack of methyltransfer to biosynthetic intermediates suggests that the reaction is the last step in the biosynthetic pathway to the oat flavonoid 7-O-methylvitexin 2"-O-rhamnoside. Based on results obtained from kinetic inhibition studies and affinity chromatography a mono-iso Theorell-Chance mechanism is proposed with the nucleotide substrate binding before the flavonoid.
已从燕麦初生叶片中分离出一种O-甲基转移酶，该酶催化S-腺苷-L-甲硫氨酸的甲基转移至牡荆素2″-O-鼠李糖苷的A环7-羟基上，并通过用硫酸铵进行蛋白质分级分离以及在DEAE-纤维素和S-腺苷-L-高半胱氨酸琼脂糖上进行色谱法纯化了180倍。S-腺苷-L-甲硫氨酸和类黄酮底物的Km值分别为1.6微摩尔和15微摩尔。未向生物合成中间体进行甲基转移表明该反应是燕麦类黄酮7-O-甲基牡荆素2″-O-鼠李糖苷生物合成途径中的最后一步。基于动力学抑制研究和亲和色谱法获得的结果，提出了一种单-异Theorell-Chance机制，其中核苷酸底物在类黄酮之前结合。
