RESUMO
italic>O-methyltransferases (OMTs) are one of the key tailoring enzymes in the biosynthesis of many natural products, O-methylation can not only reduce the reactivity of natural products, but also alter their solubility, stability and biological activities. Based on the transcriptome data of Ardisia japonica, a full-length cDNA sequence of candidate OMT (termed as AjOMT1) was cloned by reverse transcription-polymerase chain reaction (RT-PCR) and expressed in Escherichia coli (E. coli) for the first time. In vitro enzyme catalytic activity assay showed that the recombinant AjOMT1 could effectively catalyze quercetin to form O-methylated products. Most importantly, AjOMT1 showed unprecedented substrate promiscuity towards structurally various compounds including flavonoids, stilbenes, coumarins, alkaloids and phenylpropanoids, especially preferring to the compounds with adjacent phenolic hydroxyl groups, and showed regio-selectivity. These results suggested that AjOMT1 could be used as the tool enzyme to conduct O-methylation of different types of compounds to produce diverse active methylated products, and provide a new method for drug discovery, even universal part for synthetic biology of natural products.
RESUMO
Objective: In order to obtain new glycosyltransferases with highly efficient catalysis, the glycosyltransferases from Carthamus tinctorius which contains diverse types of glycosides were mined. Methods: A new glycosyltransferase gene (UGT88B2) with full length was obtained by PCR and further transformed into Escherichia coli for heterologous expression. The catalytic activity of recombinant UGT88B2 was determined by HPLC-MSn. The structures of representative catalytic products were elucidated by MS and NMR. Results: UGT88B2 exhibited catalytic promiscuity and various patterns in glycosylation of flavonoids with high efficiency. Conclusion: A new glycosyltransferase named UGT88B2 was successfully mined and can be employed as enzymatic tools in glycosylation of flavonoids.