Muzac I, Wang J, Anzellotti D, Zhang H, Ibrahim R K
Plant Biochemistry Laboratory, Concordia University, Montreal, H3G 1M8, Canada.
Arch Biochem Biophys. 2000 Mar 15;375(2):385-8. doi: 10.1006/abbi.1999.1681.
We report that the cDNA clone (Accession No. U70424), previously isolated from Arabidopsis thaliana as encoding a caffeic acid/5-hydroxyferulic acid O-methyltransferase (OMT) (1), has now been overexpressed in Escherichia coli BL21 and its recombinant protein identified as a novel flavonol 3'-OMT. It is, therefore, renamed AtOMT1. This cDNA clone has previously been identified on the basis of its 88% amino acid sequence similarity and 80% identity to the aspen bispecific lignin OMT (2), the type member of the group involved in lignin biosynthesis. Our data indicate that this novel OMT uses the flavonol quercetin as the preferred substrate, but neither of the hydroxycinnamic acids, caffeic or 5-hydroxyferulic, to any significant extent. This indicates that the high sequence similarity/identity of AtOMT1 to that of the aspen lignin OMT (2) is not sufficient to assign the function of this gene product.
我们报告，之前从拟南芥中分离出的编码咖啡酸/5-羟基阿魏酸O-甲基转移酶（OMT）的cDNA克隆（登录号U70424）（1），现已在大肠杆菌BL21中过表达，其重组蛋白被鉴定为一种新型黄酮醇3'-OMT。因此，将其重新命名为AtOMT1。该cDNA克隆先前是基于其与杨树双特异性木质素OMT（2）88%的氨基酸序列相似性和80%的一致性而鉴定出来的，杨树双特异性木质素OMT是参与木质素生物合成的该类成员中的典型成员。我们的数据表明，这种新型OMT以黄酮醇槲皮素作为首选底物，但对咖啡酸或5-羟基阿魏酸这两种羟基肉桂酸均无显著作用。这表明AtOMT1与杨树木质素OMT（2）的高序列相似性/一致性不足以确定该基因产物的功能。
