earticle

영어

Methylation and glycosylation are two different but vital modification processes in plants to generate diversified secondary metabolites. Methylation increases the lipophilicity of compounds whereas glycosylation enhances the solubility. Most of the methylated and glycosylated natural compounds are significantly active against pathogens and cancers. In this study, an O-methyltransferase gene, designated as SpOMT-2884, was identified from Streptomyces peucetius ATCC 27952. To find the exact substrates for SpOMT-2884, we tested several compounds in-vitro. As a result SpOMT-2884 catalyzed O-methylation of flavonoids such a 7,8-dihydroxyflavone (7,8-DHF), quercetin, luteolin, fisetin and rutin. 7,8-DHF was found to be the best substrate. We further proceeded for in vivo biotransformation of 7,8-DHF where we used E. coli BL21 (DE3) expressing SpOMT-2884 cell, as a biocatalyst for the production of methylated derivative of 7,8-DHF. The supplementation of 0.2 mM of 7, 8-DHF in the growing induced culture of E.coli BL21 (DE3) harboring pET28-SpOMT-2884 recombinant resulted in the production of 7-methyl-8-hydroxyflavone which was confirmed by HPLC (Rt: 17 min), high resolution LC-QTOF-ESI/MS (m/z+ 269.08) and NMR spectroscopy. Further, this enzymatically synthesized methylated derivative of 7, 8-DHF was used as a substrate in vitro for glycosylation by Yjic, a glycosyltransferase from Bacillus licheniformis DSM13. This in-vitro reaction mixture analysis revealed the presence of glycosylated product which was confirmed by HPLC and LC-QTOF-ESI/MS (m/z+ 431.13). The glycosylation of the target was further supported by our findings from in silico docking analysis. Inparticular, this study demonstrated the potential for enzymatic biosynthesis of novel methylated cum glycosylated 7,8-DHF.